Shear bond resistance and enamel surface comparison after the bonding and debonding of ceramic and metallic brackets

PubMed Central

da Rocha, José Maurício; Gravina, Marco Abdo; Campos, Marcio José da Silva; Quintão, Cátia Cardoso Abdo; Elias, Carlos Nelson; Vitral, Robert Willer Farinazzo

2014-01-01

Objective To evaluate, in vitro, the shear bond strength presented by three brands of polycrystalline ceramic brackets and one brand of metallic bracket; verify the adhesive remnant index (ARI) after the tests, and analyze, through scanning electron microscopy (SEM) the enamel surface topography after debonding, detecting the release of mineral particles. Methods Sixty bovine lower incisors were used. Three ceramic brackets (Allure®, InVu®, and Clarity®) and one metallic bracket (Geneus®) were bonded with Transbond XT®. Kruskal-Wallis's test (significance level set at 5%) was applied to the results of share bond and ARI. Mann Whitney's test was performed to compare the pairs of brackets in relation to their ARI. Brown-Forsythe's test (significance level set at 5%) was applied to the results of enamel chemical composition. Comparisons between groups were made with Games-Howell's and the Post-hoc tests. Results No statistically significant difference was observed in relation to the shear bond strength loads. Clarity® brackets were the most affected in relation to the surface topography and to the release of mineral particles of enamel (calcium ions). Conclusion With regard to the ARI, there was a prevalence of score 4 (40.4%). As for enamel surface topography, the Geneus® bracket was the only one which did not show superficial tissue loss. The InVu® and Clarity® ones showed cohesive fractures in 33.3% and the Allure® in 50%, the latter being the one that presented most fractures during removal. PMID:24713563

Formation and evolution of radial fracture systems on Venus

NASA Technical Reports Server (NTRS)

Parfitt, E. A.; Head, James W.

1993-01-01

A survey of approximately 90 percent of the surface of Venus using Magellan data has been carried out to locate all radial fracture systems and to assess their association with other features such as volcanic edifices and coronae. Squyres et al. and Stofan et al. have discussed the association of radial fracture features in relation to coronae features, our approach was to assess the associations of all of the fracture systems. These fracture systems have two broad types of form - some fracture systems are associated with updomed topography, radiate from a point and have relatively uniform fracture lengths while others have a wider range of fracture lengths and radiate from the outer edge of a central caldera. Squyres et al. and Stofan et al. have interpreted both types of feature as reflecting tectonic fracturing resulting from uplift of the surface as a mantle plume impinges upon the crust. While it is true that a number of features are related to uplift and that such uplift will induce stresses consistent with radial fracturing, we explore the possibility that these fractures are not exclusively of tectonic origin. Purely tectonic fracturing will tend to generate a few main fractures/faults along which most of the stresses due to uplift will be accommodated leading to the triple-junction form common for terrestrial updoming. Though this type of feature is observed on Venus (e.g., feature located at 34S86), the majority of radial fracture systems display much more intensive fracturing than this through a full 360 degrees; this is difficult to explain by purely tectonic processes. The association of many of the fractures with radial lava flows leads us to interpret these fractures as reflecting dike emplacement: the form of the fractures being consistent with primarily vertical propagation from the head of a mantle plume. In the case of the second type of fracture system (those radiating from a central caldera), an even stronger case can be made that the fractures are not of tectonic origin. These features are not as commonly associated with updoming of the surface and where they are, the fractures extend out well beyond the edge of the topographic rise - an observation which is not consistent with the fractures being of tectonic uplift origin. Furthermore the fractures have a distribution of lengths (many short, fewer long) which is characteristic of dike swarms, and show direct associations with calderas and lava flows consistent with a volcanic origin. In addition, the longest fractures have a radial pattern only close to the center of the system but bend with distance to align themselves with the regional stress field - this behavior is very difficult to explain on purely tectonic grounds but is a pattern commonly seen for terrestrial dikes. For these reasons, we argue that many, if not the majority, of radial fracture systems found on Venus are the surface reflection of dike swarms, those associated with positive topography reflecting vertical emplacement and those radiating from calderas reflecting lateral propagation.

Fathoms Below: Propagation of Deep Water-driven Fractures and Implications for Surface Expression and Temporally-varying Activity at Europa

NASA Astrophysics Data System (ADS)

Walker, C. C.; Craft, K.; Schmidt, B. E.

2015-12-01

The fracture and failure of Europa's icy shell are not only observable scars of variable stress and activity throughout its evolution, they also serve key as mechanisms in the interaction of surface and subsurface material, and thus crucial aspects of the study of crustal overturn and ice shell habitability. Galileo images, our best and only reasonable-resolution views of Europa until the Europa Multiple Flyby Mission arrives in the coming decades, illustrates a single snapshot in time in Europa's history from which we deduce many temporally-based hypotheses. One of those hypotheses, which we investigate here, is that sub-surface water-both in the form of Great Lake-sized perched water pockets in the near-surface and the larger global ocean below-drives the deformation, fracture, and failure of the surface. Using Galileo's snapshot in time, we use a 2D/3D hydraulic fracturing model to investigate the propagation of vertical fractures upward into the ice shell, motion of water within and between fractures, and the subsequent break-up of ice over shallow water, forming the chaos regions and other smaller surface features. We will present results from a cohesive fragmentation model to determine the time over which chaos formation occurs, and use a fracking model to determine the time interval required to allow water to escape from basal fractures in the ice shell. In determining the style, energy, and timescale of these processes, we constrain temporal variability in observable activity and topography at the surface. Finally, we compare these results to similar settings on Earth-Antarctica-where we have much higher resolution imagery and observations to better understand how sub-surface water can affect ice surface morphology, which most certainly have implications for future flyby and surface lander exploration.

Effects of aperture variability and wettability on immiscible displacement in fractures

NASA Astrophysics Data System (ADS)

Yang, Zhibing; Méheust, Yves; Neuweiler, Insa

2017-04-01

Fluid-fluid displacement in porous and fractured media is an important process. Understanding and controlling this process is key to many practical applications, such as hydrocarbon recovery, geological storage of CO2, groundwater remediation, etc. Here, we numerically study fluid-fluid displacement in rough-walled fractures. We focus on the combined effect of wettability and fracture surface topography on displacement patterns and interface growth. We develop a novel numerical model to simulate dynamic fluid invasion under the influence of capillary and viscous forces. The capillary force is calculated using the two principal curvatures (aperture-induced curvature and in-plane curvature) at the fluid-fluid interface, and the viscous force is taken into account by solving the fluid pressure distribution. The aperture field of a fracture is represented by a spatially correlated random field, which is described by a power spectrum for the fracture wall topography and a cutoff wave-length. We numerically produce displacement patterns ranging from stable displacement, capillary fingering, and viscous fingering, as well as the transitions between them. We show that both reducing the aperture variability and increasing the contact angle (from drainage to weak imbibition) stabilize the displacement due to the influence of the in-plane curvature, an effect analogous to that of the cooperative pore filling in porous media. Implications of these results will be discussed.

Influence of surface finishing on fracture load and failure mode of glass ceramic crowns.

PubMed

Mores, Rafael Tagliari; Borba, Márcia; Corazza, Pedro Henrique; Della Bona, Álvaro; Benetti, Paula

2017-10-01

Ceramic restorations often require adjustments using diamond rotary instruments, which damage the glazed surface. The effect of these adjustments on the fracture behavior of these restorations is unclear. The purpose of this in vitro study was to evaluate the influence of induced surface defects on the fracture load and mode of failure of lithium disilicate-based (LDS) glass ceramic restorations. Premolar crowns were obtained from LDS computer-aided design and computer-aided manufacturing blocks (n=60) and glazed. The crowns were bonded to dentin analog dies and divided into 5 groups (n=12), as follows: glaze; abrasion (diamond rotary instrument 2135); abrasion and reglaze; abrasion and polishing (diamond rotary instrument 2135F, 2135 FF, and polishing devices); and polishing. The topography of the crowns was examined by scanning electron microscopy, and roughness was measured. A compressive load (0.5 mm/min) was applied by a piston to the center of the lingual cusp until fracture. The fracture load was recorded and data were statistically analyzed by ANOVA and the Tukey HSD test (α=.05). Fractured crowns were examined to determine the fracture origin. Polishing and/or reglazing resulted in lower roughness than for the abraded group (P<.05), which did not affect the fracture loads (P=.696). Catastrophic fracture with origin at the intaglio surface was the mode of failure for all the crowns. The experiment design successfully submitted the crowns to a clinical stress state, resulting in a clinically relevant failure. Reglazing or polishing were effective in reducing surface defects. Surface treatments had no effect on the immediate catastrophic failure of LDS crowns. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Fractographic ceramic failure analysis using the replica technique

PubMed Central

Scherrer, Susanne S.; Quinn, Janet B.; Quinn, George D.; Anselm Wiskott, H. W.

2007-01-01

Objectives To demonstrate the effectiveness of in vivo replicas of fractured ceramic surfaces for descriptive fractography as applied to the analysis of clinical failures. Methods The fracture surface topography of partially failed veneering ceramic of a Procera Alumina molar and an In Ceram Zirconia premolar were examined utilizing gold-coated epoxy poured replicas viewed using scanning electron microscopy. The replicas were inspected for fractographic features such as hackle, wake hackle, twist hackle, compression curl and arrest lines for determination of the direction of crack propagation and location of the origin. Results For both veneering ceramics, replicas provided an excellent reproduction of the fractured surfaces. Fine details including all characteristic fracture features produced by the interaction of the advancing crack with the material's microstructure could be recognized. The observed features are indicators of the local direction of crack propagation and were used to trace the crack's progression back to its initial starting zone (the origin). Drawbacks of replicas such as artifacts (air bubbles) or imperfections resulting from inadequate epoxy pouring were noted but not critical for the overall analysis of the fractured surfaces. Significance The replica technique proved to be easy to use and allowed an excellent reproduction of failed ceramic surfaces. It should be applied before attempting to remove any failed part remaining in situ as the fracture surface may be damaged during this procedure. These two case studies are intended as an introduction for the clinical researcher in using qualitative (descriptive) fractography as a tool for understanding fracture processes in brittle restorative materials and, secondarily, to draw conclusions as to possible design inadequacies in failed restorations. PMID:17270267

Buried topography of Utopia, Mars - Persistence of a giant impact depression

NASA Technical Reports Server (NTRS)

Mcgill, George E.

1989-01-01

Knobs, partially buried craters, ring fractures, and some mesas permit a qualitative determination of the topography buried beneath younger northern plains materials. These features are widely distributed in the Utopia area but are absent in a large, roughly circular region centered at about 48 deg N, 240 deg W. This implies the existence of a circular depression about 3300 km in diameter buried beneath Utopia Planitia that is interpreted to represent the central part of a very large impact basin. The presence of buried curved massifs around part of this depression, and a roughly coincident mascon, lend further support. Present topography, areal geology, and paleotopography of buried surfaces all point to the persistence of this major depression for almost the entire history of Mars.

Low surface gravitational acceleration of Mars results in a thick and weak lithosphere: Implications for topography, volcanism, and hydrology

NASA Astrophysics Data System (ADS)

Heap, Michael J.; Byrne, Paul K.; Mikhail, Sami

2017-01-01

Surface gravitational acceleration (surface gravity) on Mars, the second-smallest planet in the Solar System, is much lower than that on Earth. A direct consequence of this low surface gravity is that lithostatic pressure is lower on Mars than on Earth at any given depth. Collated published data from deformation experiments on basalts suggest that, throughout its geological history (and thus thermal evolution), the Martian brittle lithosphere was much thicker but weaker than that of present-day Earth as a function solely of surface gravity. We also demonstrate, again as a consequence of its lower surface gravity, that the Martian lithosphere is more porous, that fractures on Mars remain open to greater depths and are wider at a given depth, and that the maximum penetration depth for opening-mode fractures (i.e., joints) is much deeper on Mars than on Earth. The result of a weak Martian lithosphere is that dykes-the primary mechanism for magma transport on both planets-can propagate more easily and can be much wider on Mars than on Earth. We suggest that this increased the efficiency of magma delivery to and towards the Martian surface during its volcanically active past, and therefore assisted the exogeneous and endogenous growth of the planet's enormous volcanoes (the heights of which are supported by the thick Martian lithosphere) as well as extensive flood-mode volcanism. The porous and pervasively fractured (and permeable) nature of the Martian lithosphere will have also greatly assisted the subsurface storage of and transport of fluids through the lithosphere throughout its geologically history. And so it is that surface gravity, influenced by the mass of a planetary body, can greatly modify the mechanical and hydraulic behaviour of its lithosphere with manifest differences in surface topography and geomorphology, volcanic character, and hydrology.

Investigation of diamond wheel topography in Elliptical Ultrasonic Assisted Grinding (EUAG) of monocrystal sapphire using fractal analysis method.

PubMed

Wang, Qiuyan; Zhao, Wenxiang; Liang, Zhiqiang; Wang, Xibin; Zhou, Tianfeng; Wu, Yongbo; Jiao, Li

2018-03-01

The wear behaviors of grinding wheel have significant influence on the work-surface topography. However, a comprehensive and quantitative method is lacking for evaluating the wear conditions of grinding wheel. In this paper, a fractal analysis method is used to investigate the wear behavior of resin-bonded diamond wheel in Elliptical Ultrasonic Assisted Grinding (EUAG) of monocrystal sapphire, and a series of experiments on EUAG and conventional grinding (CG) are performed. The results show that the fractal dimension of grinding wheel topography is highly correlated to the wear behavior, i.e., grain fracture, grain pullout, and wheel loading. An increase in cutting edge density on the wheel surface results in an increase of the fractal dimension, but an increase in the grain pullout and wheel loading results in a decrease in the fractal dimension. The wheel topography in EUAG has a higher fractal dimension than that in CG before 60 passes due to better self-sharpening behavior, and then has a smaller fractal dimension because of more serious wheel loadings after 60 passes. By angle-dependent distribution analysis of profile fractal dimensions, the wheel surface topography is transformed from isotropic to anisotropic. These indicated that the fractal analysis method could be further used in monitoring of a grinding wheel performance in EUAG. Copyright © 2017 Elsevier B.V. All rights reserved.

Reducing Ice Adhesion on Nonsmooth Metallic Surfaces: Wettability and Topography Effects.

PubMed

Ling, Edwin Jee Yang; Uong, Victor; Renault-Crispo, Jean-Sébastien; Kietzig, Anne-Marie; Servio, Phillip

2016-04-06

The effects of ice formation and accretion on external surfaces range from being mildly annoying to potentially life-threatening. Ice-shedding materials, which lower the adhesion strength of ice to its surface, have recently received renewed research attention as a means to circumvent the problem of icing. In this work, we investigate how surface wettability and surface topography influence the ice adhesion strength on three different surfaces: (i) superhydrophobic laser-inscribed square pillars on copper, (ii) stainless steel 316 Dutch-weave meshes, and (iii) multiwalled carbon nanotube-covered steel meshes. The finest stainless steel mesh displayed the best performance with a 93% decrease in ice adhesion relative to polished stainless steel, while the superhydrophobic square pillars exhibited an increase in ice adhesion by up to 67% relative to polished copper. Comparisons of dynamic contact angles revealed little correlation between surface wettability and ice adhesion. On the other hand, by considering the ice formation process and the fracture mechanics at the ice-substrate interface, we found that two competing mechanisms governing ice adhesion strength arise on nonplanar surfaces: (i) mechanical interlocking of the ice within the surface features that enhances adhesion, and (ii) formation of microcracks that act as interfacial stress concentrators, which reduce adhesion. Our analysis provides insight toward new approaches for the design of ice-releasing materials through the use of surface topographies that promote interfacial crack propagation.

Smoothing and roughening of slip surfaces in direct shear experiments

NASA Astrophysics Data System (ADS)

Sagy, Amir; Badt, Nir; Hatzor, Yossef H.

2015-04-01

Faults in the upper crust contain discrete slip surfaces which have absorbed a significant part of the shear displacement along them. Field measurements demonstrate that these surfaces are rough at all measurable scales and indicate that surfaces of relatively large-slip faults are statistically smoother than those of small-slip faults. However, post faulting and surface erosion process that might affect the geometry of outcrops cannot be discounted in such measurements. Here we present experimental results for the evolution of shear surface topography as function of slip distance and normal stress in direct shear experiments. A single prismatic fine grain limestone block is first fractured in tension mode using the four-point bending test methodology and then the fracture surface topography is scanned using a laser profilometer. We then shear the obtained tensile fracture surfaces in direct shear, ensuring the original fracture surfaces are in a perfectly matching configuration at the beginning of the shear test. First, shearing is conducted to distances varying from 5 to 15 mm under constant normal stress of 2MPa and a constant displacement rate of 0.05 mm/s using two closed-loop servo controlled hydraulic pistons, supplying normal and shear forces (Davidesko et al., 2014). In the tested configuration peak shear stress is typically attained after a shear displacement of about 2-3 mm, beyond which lower shear stress is required to continue shearing at the preset displacement rate of 0.05 mm/s as is typical for initially rough joints. Following some initial compression the interface begins to dilate and continues to do so until the end of the test. The sheared tensile fracture surface is then scanned again and the geometrical evolution, in term of RMS roughness and power spectral density (PSD) is analyzed. We show that shearing smooth the surface along all our measurements scales. The roughness ratio, measured by initial PSD / final PSD for each wavelength, increases as a function of slip amount. The roughness measured after slip can be fitted by a power-law similar to that of the initial tensile surface. In the next series of experiments a similar procedure is applied when the roughness evolution is measured as a function of increasing normal stress for a fixed displacement amount of 10 mm. While samples sheared under a constant normal stress of 5 MPa generated surface smoothing, shearing under normal stress of 7.5 MPa to 15 MPa exhibited surface roughening at the measured range of scales. We find that roughening is correlated with the attained peak shear stress values, stress drop (peak shear stress minus residual shear stress) and with wear accumulation, a novel measurement procedure of which is developed here. Analysis of the sheared samples shows that roughening is generated by sets of dense fractures that significantly damaged the sample in the immediate proximity to large asperities. This roughening is related to penetrative damage during transient wear in rough surfaces.

Fractographic correlations with mechanical properties in ferritic martensitic steels

NASA Astrophysics Data System (ADS)

Das, Arpan; Chakravartty, Jayanta Kumar

2017-12-01

The ultimate continuum of a material is nothing but the process called fracture. Fracture surface retains the imprint of the entire deformation history undergone in a material. Hence, it is possible to derive the approximate deformation and fracture properties of a material from a systematic fracture feature analysis. There has been large volume of literature available in the open domain correlating different mechanical and fracture responses of reduced activation ferritic martensitic grade steels under various testing conditions/circumstances with corresponding microstructural interpretation. There has been no such literature available to establish the relationship between the two-dimensional fracture geometry/topography with its corresponding deformation and mechanical properties of the material as a function of testing temperature, which has been the primary aim in the current investigation. A comprehensive literature survey has been carried out to realize this fact. In order to establish the above hypothesis, many tensile experiments were carried out at constant strain rate by systematic variation of the test temperature. The initial void volume fraction or the inclusion content of material was kept unaltered and the test temperature has been varied orderly on different multiple specimens to vary the deformation-induced nucleation sites of micro voids (i.e. different carbides, phase interfaces, dislocation pile up etc), which results in a change of fracture topography under uniaxial tensile deformation. A conventional metallographic technique followed by optical microscopy has been employed to understand the basic morphologies and characteristics of the alloy exposed at different temperatures. Fractographic investigation of the broken tensile specimens at various temperatures is carried out to measure the fracture features by using quantitative fractography on representative scanning electron fractographs through image processing.

Stiffness of the endplate boundary layer and endplate surface topography are associated with brittleness of human whole vertebral bodies

PubMed Central

Nekkanty, Srikant; Yerramshetty, Janardhan; Kim, Do-Gyoon; Zauel, Roger; Johnson, Evan; Cody, Dianna D.; Yeni, Yener N.

2013-01-01

Stress magnitude and variability as estimated from large scale finite element (FE) analyses have been associated with compressive strength of human vertebral cancellous cores but these relationships have not been explored for whole vertebral bodies. In this study, the objectives were to investigate the relationship of FE-calculated stress distribution parameters with experimentally determined strength, stiffness, and displacement based ductility measures in human whole vertebral bodies, investigate the effect of endplate loading conditions on vertebral stiffness, strength, and ductility and test the hypothesis that endplate topography affects vertebral ductility and stress distributions. Eighteen vertebral bodies (T6-L3 levels; 4 female and 5 male cadavers, aged 40-98 years) were scanned using a flat panel CT system and followed with axial compression testing with Wood’s metal as filler material to maintain flat boundaries between load plates and specimens. FE models were constructed using reconstructed CT images and filler material was added digitally. Two different FE models with different filler material modulus simulating Wood’s metal and intervertebral disc (W-layer and D-layer models) were used. Element material modulus to cancellous bone was based on image gray value. Average, standard deviation, and coefficient of variation of von Mises stress in vertebral bone for W-layer and D-layer models and also the ratios of FE parameters from the two models (W/D) were calculated. Inferior and superior endplate surface topographical distribution parameters were calculated. Experimental stiffness, maximum load and work to fracture had the highest correlation with FE-calculated stiffness while experimental ductility measures had highest correlations with FE-calculated average von Mises stress and W-layer to D-layer stiffness ratio. Endplate topography of the vertebra was also associated with its structural ductility and the distribution parameter that best explained this association was kurtosis of inferior endplate topography. Our results indicate that endplate topography variations may provide insight into the mechanisms responsible for vertebral fractures. PMID:20633709

Induced stress changes and associated fracture development as a result of deglaciation on the Zugspitzplatt, SE Germany

NASA Astrophysics Data System (ADS)

Leith, Kerry; Kupp, Jan; Geisenhof, Benedikt; Krautblatter, Michael

2015-04-01

Bedrock stresses in alpine regions result from the combined effects of exhumation, tectonics, topography, inelastic strain (e.g. fault displacement and fracture formation), and external loading. Gravitational loading by glacial ice can significantly affect near-surface stress magnitudes, although the nature of this effect and it's impact on stress distributions and bedrock fracturing is strongly dependent on the stress history of the bedrock landscape. We assess the effects of recent (post-Little Ice Age , ~1850 AD) and future deglaciation on bedrock stresses in the region of the Zugspitzplatt, a glaciated plateau surrounded by 1500 m high bedrock walls in SE Germany. We address this by undertaking a 2-D elasto-plastic finite element method analysis of stress changes and fracture propagation due to repeated glacial - interglacial cycles. Our model is initialised with upper crustal stresses in equilibrium with bedrock strength and regional tectonics, and we then simulate two cycles of major Pleistocene glaciation and deglaciation in order to dissipate stress concentrations and incorporate path-dependent effects of glacial loading on the landscape. We then simulate a final glacial cycle, and remove 1 m of bedrock to approximate glacial erosion across the topography. Finally, ice levels are reduced in accordance with known late-glacial and recent ice retreat, allowing us to compare relative stress changes and predicted patterns of fracture propagation to observed fracture distributions on the Zugspitzplatt. Model results compare favourably to observed fracture patterns, and indicate the plateau is likely to be undergoing N-S extension as a result of deglaciation, with a strong reduction of horizontal stress magnitudes beneath the present-day Schneeferner glacier. As each glacial cycle has a similar effect on the plateau, it is likely that surficial stresses are slightly tensile, and each cycle of deglaciation produces additional sub-vertical tensile fractures, which are then exploited by the karst groundwater system. Here we show how stress histories and brittle deformation in near-surface stress models can provide a better understanding of long-term rock slope evolution and failure as well as karst co-evolution in Alpine Environments.

Signatures of Lithospheric Flexure and Elevated Heat Flow in Stereo Topography at Coronae on Venus

NASA Astrophysics Data System (ADS)

O'Rourke, Joseph G.; Smrekar, Suzanne E.

2018-02-01

Signatures of lithospheric flexure were previously identified at a dozen or more large coronae on Venus. Thin plate models fit to topographic profiles return elastic parameters, allowing derivation of mechanical thickness and surface heat flows given an assumed yield strength envelope. However, the low resolution of altimetry data from the NASA Magellan mission has hindered studying the vast majority of coronae, particularly those less than a few hundred kilometers in diameter. Here we search for flexural signatures around 99 coronae over ˜20% of the surface in Magellan altimetry data and stereo-derived topography that was recently assembled from synthetic aperture radar images. We derive elastic thicknesses of ˜2 to 30 km (mostly ˜5 to 15 km) with Cartesian and axisymmetric models at 19 coronae. We discuss the implications of low values that were also noted in earlier gravity studies. Most mechanical thicknesses are estimated as <19 km, corresponding to thermal gradients >24 K km-1. Implied surface heat flows >95 mW m-2—twice the global average in many thermal evolution models—imply that coronae are major contributors to the total heat budget or Venus is cooling faster than expected. Binomial statistics show that "Type 2" coronae with incomplete fracture annuli are significantly less likely to host flexural signatures than "Type 1" coronae with largely complete annuli. Stress calculations predict extensional faulting where nearly all profiles intersect concentric fractures. We failed to identify systematic variations in flexural parameters based on type, geologic setting, or morphologic class. Obtaining quality, high-resolution topography from a planetwide survey is vital to verifying our conclusions.

Geologic Map of the Diana Chasma Quadrangle (V-37), Venus

USGS Publications Warehouse

Hansen, V.L.; DeShon, H.R.

2002-01-01

Diana Chasma quadrangle hosts some of the steepest topography on Venus. Altimetry measurements range from -2.5 to 4.7 km (0.0 = mean planetary radius), with a surface mean of 0.6 km. Fractures and faults within the central fracture/rift zone create large blocks of down-dropped material, especially along the east-central edge of the map area. The Dali and Diana chasmata display slopes of >30°, the steepest and deepest trenches on Venus. Both chasmata host landslide deposits presumably sourced from the steep chasmata walls. The tessera inlier, coronae, and ridge belts sit topographically above Rusalka and Zhibek planitiae. Rusalka Planitia topography describes broad undulations having northwest-trending ridges spaced ~200 km apart. The most distinctive ridge, Vetsorgo Dorsum, centered at 6.5° S., 163° E., is a Class I ridge belt owing to its simple arch morphology. The central interior of Markham crater sits topographically lower than the surrounding region, which slopes downward to the east.

Cryo-planing of frozen-hydrated samples using cryo triple ion gun milling (CryoTIGM™).

PubMed

Chang, Irene Y T; Joester, Derk

2015-12-01

Cryo-SEM is a high throughput technique for imaging biological ultrastructure in its most pristine state, i.e. without chemical fixation, embedding, or drying. Freeze fracture is routinely used to prepare internal surfaces for cryo-SEM imaging. However, the propagation of the fracture plane is highly dependent on sample properties, and the resulting surface frequently shows substantial topography, which can complicate image analysis and interpretation. We have developed a broad ion beam milling technique, called cryogenic triple ion gun milling (CryoTIGM™ ['krī-ə-,tīm]), for cryo-planing frozen-hydrated biological specimens. Comparing sample preparation by CryoTIGM™ and freeze fracture in three model systems, Baker's yeast, mouse liver tissue, and whole sea urchin embryos, we find that CryoTIGM™ yields very large (∼700,000 μm(2)) and smooth sections that present ultrastructural details at similar or better quality than freeze-fractured samples. A particular strength of CryoTIGM™ is the ability to section samples with hard-soft contrast such as brittle calcite (CaCO3) spicules in the sea urchin embryo. Copyright © 2015 Elsevier Inc. All rights reserved.

The influence of Y-TZP surface treatment on topography and ceramic/resin cement interfacial fracture toughness.

PubMed

Paes, P N G; Bastian, F L; Jardim, P M

2017-09-01

Consider the efficacy of glass infiltration etching (SIE) treatment as a procedure to modify the zirconia surface resulting in higher interfacial fracture toughness. Y-TZP was subjected to 5 different surface treatments conditions consisting of no treatment (G1), SIE followed by hydrofluoric acid treatment (G2), heat treated at 750°C (G3), hydrofluoric acid treated (G4) and airborne-particle abrasion with alumina particles (G5). The effect of surface treatment on roughness was evaluated by Atomic Force Microscopy providing three different parameters: R a , R sk and surface area variation. The ceramic/resin cement interface was analyzed by Fracture Mechanics K I test with failure mode determined by fractographic analysis. Weibull's analysis was also performed to evaluate the structural integrity of the adhesion zone. G2 and G4 specimens showed very similar, and high R a values but different surface area variation (33% for G2 and 13% for G4) and they presented the highest fracture toughness (K IC ). Weibull's analysis showed G2 (SIE) tendency to exhibit higher K IC values than the other groups but with more data scatter and a higher early failure probability than G4 specimens. Selective glass infiltration etching surface treatment was effective in modifying the zirconia surface roughness, increasing the bonding area and hence the mechanical imbrications at the zirconia/resin cement interface resulting in higher fracture toughness (K IC ) values with higher K IC values obtained when failure probability above 20% was expected (Weibull's distribution) among all the experimental groups. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of core ceramic grinding on fracture behaviour of bilayered zirconia veneering ceramic systems under two loading schemes.

PubMed

Jian, Yu-Tao; Tang, Tian-Yu; Swain, Michael V; Wang, Xiao-Dong; Zhao, Ke

2016-12-01

The aim of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered zirconia under two loading schemes. Interfacial surfaces of sandblasted zirconia disks (A) were ground with 80 (B), 120 (C) and 220 (D) grit diamond discs, respectively. Surface roughness and topographic analysis were performed using a confocal scanning laser microscope (CSLM) and a scanning electron microscopy (SEM). Relative monoclinic content was evaluated using X-ray diffraction analysis (XRD) then reevaluated after simulated veneer firing. Biaxial fracture strength (σ) and Weibull modulus (m) were calculated either with core in compression (subgroup Ac-Dc) or in tension (subgroup At-Dt). Facture surfaces were examined by SEM and energy dispersive X-ray spectroscopy (EDS). Maximum tensile stress at fracture was estimated by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis and one-way ANOVA at a significance level of 0.05. As grit size of the diamond disc increased, zirconia surface roughness decreased (p<0.001). Thermal veneering treatment reversed the transformation of monoclinic phase observed after initial grinding. No difference in initial (p=0.519 for subgroups Ac-Dc) and final fracture strength (p=0.699 for subgroups Ac-Dc; p=0.328 for subgroups At-Dt) was found among the four groups for both loading schemes. While coarse grinding slightly increased final fracture strength reliability (m) for subgroups Ac-Dc. Two different modes of fracture were observed according to which material was on the bottom surface. Components of the liner porcelain remained on the zirconia surface after fracture for all groups. Technician grinding changed surface topography of zirconia ceramic material, but was not detrimental to the bilayered system strength after veneer application. Coarse grinding slightly improved the fracture strength reliability of the bilayered system tested with core in compression. It is recommended that veneering porcelain be applied directly after routine lab grinding of zirconia ceramic, and its application on rough zirconia cores may be preferred to enhance bond strength. Copyright © 2016. Published by Elsevier Ltd.

Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Höfner, S.; Vincent, J.-B.; Blum, J.; Davidsson, B. J. R.; Sierks, H.; El-Maarry, M. R.; Deller, J.; Hofmann, M.; Hu, X.; Pajola, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Auger, A.-T.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marqués, P.; Güttler, C.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Michalik, H.; Moissl-Fraund, R.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.; Zitzmann, S.

2017-12-01

Context. The camera OSIRIS on board Rosetta obtained high-resolution images of the nucleus of comet 67P/Churyumov-Gerasimenko (67P). Great parts of the nucleus surface are composed of fractured terrain. Aims: Fracture formation, evolution, and their potential relationship to physical processes that drive activity are not yet fully understood. Observed temperatures and gas production rates can be explained or interpreted with the presence of fractures by applying appropriate modelling methods. Methods: We followed a transient thermophysical model approach that includes radiative, conductive, and water-ice sublimation fluxes by considering a variety of heliocentric distances, illumination conditions, and thermophysical properties for a set of characteristic fracture geometries on the nucleus of 67P. We computed diurnal temperatures, heat fluxes, and outgassing behaviour in order to derive and distinguish the influence of the mentioned parameters on fractured terrain. Results: Our analysis confirms that fractures, as already indicated by former studies about concavities, deviate from flat-terrain topographies with equivalent properties, mostly through the effect of self-heating. Compared to flat terrain, illuminated cometary fractures are generally warmer, with smaller diurnal temperature fluctuations. Maximum sublimation rates reach higher peaks, and dust mantle quenching effects on sublimation rates are weaker. Consequently, the rough structure of the fractured terrain leads to significantly higher inferred surface thermal inertia values than for flat areas with identical physical properties, which might explain the range of measured thermal inertia on 67P. Conclusions: At 3.5 AU heliocentric distance, sublimation heat sinks in fractures converge to maximum values >50 W / m2 and trigger dust activity that can be related mainly to H2O. Fractures are likely to grow through the erosive interplay of alternating sublimation and thermal fatigue.

The Effect of Topographic Shadowing by Ice on Irradiance in the Greenland Ice Sheet Ablation Zone

NASA Astrophysics Data System (ADS)

Leidman, S. Z.; Rennermalm, A. K.; Ryan, J.; Cooper, M. G.; Smith, L. C.

2017-12-01

Accurately predicting runoff contributions to global sea level rise requires more refined surface mass balance (SMB) models of the Greenland Ice Sheet (GrIS). Topographic shadowing has shown to be important in the SMB of snow-covered regions, yet SMB models for the GrIS generally ignore how surface topography affects spatial variability of incoming solar radiation on a surface. In the ablation zone of Southwest Greenland, deeply incised supraglacial drainage features, fracturing, and large-scale bed deformation result in extensive areas of rough surface topography. This topography blocks direct radiation such that shadowed areas receive less energy for melting while other topographic features such as peaks recieve more energy. In this study, we quantify how shadowing from local topography features changes incoming solar radiation. We apply the ArcGIS Pro Solar Radiation Toolset to calculate the direct and diffuse irradiance in sunlit and shadowed areas by determining the sun's movement for every half hour increment of 2016. Multiple digital elevation models (DEMs) with spatial resolutions ranging from 0.06 to 5m were derived from fixed wing and quadcopter UAV imagery collected in summer 2016 and the ArcticDEM dataset. Our findings show that shadowing significantly decreases irradiance compared to smoothed surfaces where local topography is removed. This decrease is exponentially proportional to the DEM pixel sized with 5m DEMs only able to capture a small percentage of the effect. Applying these calculations to the ArcticDEM to cover a larger study area indicates that decreases in irradiance are nonlinearly proportional to elevation with highly crevassed areas showing a larger effect from shadowing. Even so, shading at higher elevations reduces irradiance enough to result in several centimeters snow water equivalence (SWE) per year of over-prediction of runoff in SMB models. Furthermore, analysis of solar radiation products shows that shadowing predicts albedo variability far better than a range of variables derived from UAV imagery mosaics including slope, aspect, elevation, or the distance to dark surface features. In summary, implementation of the effect of shadowing on irradiance should therefore be considered for accurate surface mass balance calculations for the Greenland ice sheet.

A Statistical Analysis of Corona Topography: New Insights into Corona Formation and Evolution

NASA Technical Reports Server (NTRS)

Stofan, E. R.; Glaze, L. S.; Smrekar, S. E.; Baloga, S. M.

2003-01-01

Extensive mapping of the surface of Venus and continued analysis of Magellan data have allowed a more comprehensive survey of coronae to be conducted. Our updated corona database contains 514 features, an increase from the 326 coronae of the previous survey. We include a new set of 106 Type 2 or stealth coronae, which have a topographic rather than a fracture annulus. The large increase in the number of coronae over the 1992 survey results from several factors, including the use of the full Magellan data set and the addition of features identified as part of the systematic geologic mapping of Venus. Parameters of the population that we have analyzed to date include size and topography.

Characterization of the 3-D fracture setting of an unstable rock mass: From surface and seismic investigations to numerical modeling

NASA Astrophysics Data System (ADS)

Colombero, C.; Baillet, L.; Comina, C.; Jongmans, D.; Vinciguerra, S.

2017-08-01

The characterization of the fracturing state of a potentially unstable rock cliff is a crucial requirement for stability assessments and mitigation purposes. Classical measurements of fracture location and orientation can however be limited by inaccessible rock exposures. The steep topography and high-rise morphology of these cliffs, together with the widespread presence of fractures, can additionally condition the success of geophysical prospecting on these sites. In order to mitigate these limitations, an innovative approach combining noncontact geomechanical measurements, active and passive seismic surveys, and 3-D numerical modeling is proposed in this work to characterize the 3-D fracture setting of an unstable rock mass, located in NW Italian Alps (Madonna del Sasso, VB). The 3-D fracture geometry was achieved through a combination of field observations and noncontact geomechanical measurements on oriented pictures of the cliff, resulting from a previous laser-scanning and photogrammetric survey. The estimation of fracture persistence within the rock mass was obtained from surface active seismic surveys. Ambient seismic noise and earthquakes recordings were used to assess the fracture control on the site response. Processing of both data sets highlighted the resonance properties of the unstable rock volume decoupling from the stable massif. A finite element 3-D model of the site, including all the retrieved fracture information, enabled both validation and interpretation of the field measurements. The integration of these different methodologies, applied for the first time to a complex 3-D prone-to-fall mass, provided consistent information on the internal fracturing conditions, supplying key parameters for future monitoring purposes and mitigation strategies.

In situ observation of fluoride-ion-induced hydroxyapatite collagen detachment on bone fracture surfaces by atomic force microscopy

NASA Astrophysics Data System (ADS)

Kindt, J. H.; Thurner, P. J.; Lauer, M. E.; Bosma, B. L.; Schitter, G.; Fantner, G. E.; Izumi, M.; Weaver, J. C.; Morse, D. E.; Hansma, P. K.

2007-04-01

The topography of freshly fractured bovine and human bone surfaces was determined by the use of atomic force microscopy (AFM). Fracture surfaces from both kinds of samples exhibited complex landscapes formed by hydroxyapatite mineral platelets with lateral dimensions ranging from ~90 nm × 60 nm to ~20 nm × 20 nm. Novel AFM techniques were used to study these fracture surfaces during various chemical treatments. Significant topographical changes were observed following exposure to aqueous solutions of ethylenediaminetetraacetic acid (EDTA) or highly concentrated sodium fluoride (NaF). Both treatments resulted in the apparent loss of the hydroxyapatite mineral platelets on a timescale of a few seconds. Collagen fibrils situated beneath the overlying mineral platelets were clearly exposed and could be resolved with high spatial resolution in the acquired AFM images. Time-dependent mass loss experiments revealed that the applied agents (NaF or EDTA) had very different resulting effects. Despite the fact that the two treatments exhibited nearly identical results following examination by AFM, bulk bone samples treated with EDTA exhibited a ~70% mass loss after 72 h, whereas for the NaF-treated samples, the mass loss was only of the order of ~10%. These results support those obtained from previous mechanical testing experiments, suggesting that enhanced formation of superficial fluoroapatite dramatically weakens the protein-hydroxyapatite interfaces. Additionally, we discovered that treatment with aqueous solutions of NaF resulted in the effective extraction of noncollagenous proteins from bone powder.

Integrated geophysical study to understand the architecture of the deep critical zone in the Luquillo Critical Zone Observatory (Puerto Rico

NASA Astrophysics Data System (ADS)

Comas, X.; Wright, W. J.; Hynek, S. A.; Ntarlagiannis, D.; Terry, N.; Whiting, F.; Job, M. J.; Brantley, S. L.; Fletcher, R. C.

2016-12-01

The Luquillo Critical Zone Observatory (CZO) in Puerto Rico is characterized by a complex system of heterogeneous fractures that participate in the formation of corestones, and influence the development of a regolith by the alteration of the bedrock at very rapid weathering rates. The spatial distribution of fractures, and its influence on regolith thickness is, however, currently not well understood. In this study, we used an array of near-surface geophysical methods, including ground penetrating radar, terrain conductivity, electrical resistivity imaging and induced polarization, OhmMapper, and shallow seismic, constrained with direct methods from previous studies. These methods were combined with stress modeling to better understand: 1) changes in regolith thickness; and 2) variation of the spatial distribution and density of fractures with topography and proximity to the knickpoint. Our observations show the potential of geophysical methods for imaging variability in regolith thickness, and agree with the result of a stress model showing increased dilation of fractures with proximity to the knickpoint.

Homing in on sweet spots in Cretaceous Austin chalk

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, G.E.; Sonnenberg, F.P.

1993-11-29

In discussing the nature and causes of fracturing in the Cretaceous Austin chalk of south central Texas, many geologists and operators involved in horizontal drilling of the chalk consider regional rock stress as the probable main cause of the fractures. If Austin chalk fractures are mainly the result of regional extensional stress without localizing factors, then fractured sweet spots are randomly distributed and successful exploration is more or less a matter of luck, usually dependent upon the coincidental placement of a seismic line. But if local, deep-seated structure or basement topography are the main causes of sweet spots, then amore » successful exploration method would be to first delineate the basement paleo structure or topography and secondly, place a seismic line to confirm the delineated features. Finding localities of maximum fracturing and production would than be based on scientific logic rather than luck. It is the purpose of this article to present the results of an examination of these alternative causes for the Austin chalk fracturing in the hope of determining the most cost effective exploration method for the fractured chalk reservoir.« less

Self-Sustained Mode-3 Tear Controls Dynamics of Narrow Retreating Subduction Zones

NASA Astrophysics Data System (ADS)

Munch, J.; Gerya, T.; Ueda, K.

2017-12-01

The Caribbean oroclinal basin exhibits several narrow retreating slabs in an oceanic domain. The slabs show a curved shape associated to a bent topography (trench). We propose that the curvature of the topography depends on slab retreat mechanisms following mode-3 tearing at the edges of the slab (out of the plane fracture propagation). While first-order characteristics have been principally reproduced in self-sustained subduction initiation models (Gerya et al., 2015, Nature, 527, 221-225), the relevant observations have not been quantified and the exact mechanism is not understood. In this work, we study the long-term 3D evolution of narrowing oceanic subduction zones during retreat, and investigate the link between mode-3 tear and orocline formation. Numerical experiments are carried out with a thermo-mechanical 3D finite-difference code. To allow the observation of developing topography, the precise location of the internal surface and its evolution by material diffusion is tracked. Retreating subduction is facilitated via a strong age contrast between a young lithosphere window enclosed by shear zones and the surrounding lithosphere. By varying the length and thickness of the shear zones and location of the age transition, the influence of these parameters on the tearing process and the development of topography is assessed. Experiments trigger subduction initiation and slab retreat via fracture zone collapse and spontaneous paired mode-3 tear propagation within the oceanic plate interior. Narrow retreating subducting slabs form as a natural result of the spontaneous paired tearing process. A curved trench forms along with slab retreat. Topography evolution and tearing trajectory appear to be dependent on the initial shear zones and young window dimensions. We also note a strong narrowing of the slab during the retreat (several tens of kilometers over 800 km of retreat). Overall, results indicate that narrowing of retreating slabs is a self-consistent consequence of tear propagation dynamics. This plate tearing mechanism may control dynamics of other narrow retreating subduction zones worldwide.

Characterization of the NEXT Hollow Cathode Inserts After Long-Duration Testing

NASA Technical Reports Server (NTRS)

Mackey, J.; Shastry, R.; Soulas, G.

2017-01-01

Hollow dispenser cathode inserts are a critical element of electric propulsion systems, and should therefore be well understood during long term operation to ensure reliable system performance. This work destructively investigated cathode inserts from the NEXT long-duration test which demonstrated 51,184 hours of high-voltage operation, 918 kg of propellant throughput, and 35.5 MN-s of total impulse. The characterization methods used include scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction. Microscopy analysis has been performed on fractured surfaces, emission surfaces, and metallographically polished cross-sections of post-test inserts and unused inserts. Impregnate distribution, etch region thickness, impregnate chemical content, emission surface topography, and emission surface phase identification are the primary factors investigated.

Reaction-Infiltration Instabilities in Fractured and Porous Rocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ladd, Anthony

In this project we are developing a multiscale analysis of the evolution of fracture permeability, using numerical simulations and linear stability analysis. Our simulations include fully three-dimensional simulations of the fracture topography, fluid flow, and reactant transport, two-dimensional simulations based on aperture models, and linear stability analysis.

Effects of karst and geologic structure on the circulation of water and permeability in carbonate aquifers

USGS Publications Warehouse

Stringfield, V.T.; Rapp, J.R.; Anders, R.B.

1979-01-01

The results of the natural processes caused by solution and leaching of limestone, dolomite, gypsum, salt and other soluble rocks, is known as karst. Development of karst is commonly known as karstification, which may have a pronounced effect on the topography, hydrology and environment, especially where such karst features as sinkholes and vertical solution shafts extend below the land surface and intersect lateral solution passages, cavities, caverns and other karst features in carbonate rocks. Karst features may be divided into two groups: (1) surficial features that do not extend far below the surface; and (2) karst features such as sinkholes that extend below the surface and affect the circulation of water below. The permeability of the most productive carbonate aquifers is due chiefly to enlargement of fractures and other openings by circulation of water. Important controlling factors responsible for the development of karst and permeability in carbonate aquifers include: (1) climate, topography, and presence of soluble rocks; (2) geologic structure; (3) nature of underground circulation; and (4) base level. Another important factor is the condition of the surface of the carbonate rocks at the time they are exposed to meteoric water. A carbonate rock surface, with soil or relatively permeable, less soluble cover, is more favorable for initiation of karstification and solution than bare rocks. Water percolates downward through the cover to the underlying carbonate rocks instead of running off on the surface. Also, the water becomes more corrosive as it percolates through the permeable cover to the underlying carbonate rocks. Where there is no cover or the cover has been removed, the carbonate rocks become case hardened and resistant to erosion. However, in regions underlain not only by carbonate rocks but also by beds of anhydrite, gypsum and salt, such as the Hueco Plateau in southeastern New Mexico, subsurface solution may occur where water without natural acids moves down from bare rock surfaces through cracks to the beds that are more soluble than carbonate rocks. For example, in the area of Carlsbad Caverns in southeastern New Mexico, much of the water responsible for solution that formed the caverns apparently entered the groundwater system through large open fractures and did not form sinkhole topography. East of the Carlsbad Caverns, however, in the Pecos River Valley where the carbonate rocks are overlain by the less soluble Ogallala Formation of Late Tertiary age, solution began along escarpments as the Pecos River and its tributaries cut through the less soluble cover. As these escarpments retreated, sinkholes and other karst features developed. Joints or fractures are essential for initiation of downward percolation of water in compact carbonate rocks such as some Paleozoic limestone in which there is no intergranular permeability. Also joints or fractures and bedding planes may be essential in the initiation of lateral movement of water in the zone of saturation. Where conditions of recharge and discharge are favorable, groundwater may move parallel to the dip. However, the direction of movement of water in most carbonate rocks is not necessarily down dip or parallel to the dip. The general direction of movement of both surface and groundwater may be parallel to the strike in a breached anticline. Faults may restrict the lateral movement of water, especially if water-bearing beds are faulted against relatively impervious beds. Conversely, some fault may serve as avenues through which water may move as, for example, in the Cretaceous Edwards aquifer in the San Antonio area, Texas. Karst aquifers, chiefly carbonate rocks, may be placed in three groups according to water-bearing capacity. Water in aquifers of group 1 occurs chiefly in joints, fractures, and other openings that have not been enlarged by solution. The yield of wells is small. Aquifers in group 2, with low to intermediate yields, are those in which

Analysis of fractures intersecting Kahi Puka Well 1 and its relation to the growth of the island of Hawaii

USGS Publications Warehouse

Morin, R.H.; Paillet, Frederick L.

1996-01-01

As part of the Hawaii Scientific Drilling Project, Kahi Puka Well 1 penetrated about 275 m of Mauna Loa basalts overlying a sequence of Mauna Kea flow units as it was drilled and cored to a total depth of 1053 m below land surface. A borehole televiewer (BHTV) was run in most of the well in successive stages prior to casing in order to obtain magnetically oriented acoustic images of the borehole wall. A total of 283 individual fractures were identified from this log and characterized in terms of strike and dip. These data are divided into three vertical sections based upon age and volcanic source, and lower hemisphere stereographic plots identify two predominant, subparallel fracture subsets common to each section. Assuming that most of the steeply dipping fractures observed in the BHTV log are tensile features generated within basalt flows during deposition and cooling, this fracture information can be combined with models of the evolution of the island of Hawaii to investigate the depositional history of these Mauna Loa and Mauna Kea basalts over the past 400 kyr. The directions of high-angle fractures appear to be generally parallel to topography or to the coastline at the time of deposition, as is supported by surface mapping of modern flows. Consequently, an overall counterclockwise rotation of about 75?? in the strike of these fractures from the bottom to the top of the well represents a systematic change in depositional slope direction over time. We attribute the observed rotation in the orientations of the two predominant fracture subsets over the past 400 kyr to changes in the configurations of volcanic sources during shield building and to the structural interference of adjacent volcanoes that produces shifts in topographic patterns.

Analysis of fractures intersecting Kahi Puka Well 1 and its relation to the growth of the island of Hawaii

NASA Astrophysics Data System (ADS)

Morin, Roger H.; Paillet, Frederick L.

1996-05-01

As part of the Hawaii Scientific Drilling Project, Kahi Puka Well 1 penetrated about 275 m of Mauna Loa basalts overlying a sequence of Mauna Kea flow units as it was drilled and cored to a total depth of 1053 m below land surface. A borehole televiewer (BHTV) was run in most of the well in successive stages prior to casing in order to obtain magnetically oriented acoustic images of the borehole wall. A total of 283 individual fractures were identified from this log and characterized in terms of strike and dip. These data are divided into three vertical sections based upon age and volcanic source, and lower hemisphere stereographic plots identify two predominant, subparallel fracture subsets common to each section. Assuming that most of the steeply dipping fractures observed in the BHTV log are tensile features generated within basalt flows during deposition and cooling, this fracture information can be combined with models of the evolution of the island of Hawaii to investigate the depositional history of these Mauna Loa and Mauna Kea basalts over the past 400 kyr. The directions of high-angle fractures appear to be generally parallel to topography or to the coastline at the time of deposition, as is supported by surface mapping of modern flows. Consequently, an overall counterclockwise rotation of about 75° in the strike of these fractures from the bottom to the top of the well represents a systematic change in depositional slope direction over time. We attribute the observed rotation in the orientations of the two predominant fracture subsets over the past 400 kyr to changes in the configurations of volcanic sources during shield building and to the structural interference of adjacent volcanoes that produces shifts in topographic patterns.

Impact of surface porosity and topography on the mechanical behavior of high strength biomedical polymers.

PubMed

Evans, Nathan T; Irvin, Cameron W; Safranski, David L; Gall, Ken

2016-06-01

The ability to control the surface topography of orthopedic implant materials is desired to improve osseointegration but is often at the expense of mechanical performance in load bearing environments. Here we investigate the effects of surface modifications, roughness and porosity, on the mechanical properties of a set of polymers with diverse chemistry and structure. Both roughness and surface porosity resulted in samples with lower strength, failure strain and fatigue life due to stress concentrations at the surface; however, the decrease in ductility and fatigue strength were greater than the decrease in monotonic strength. The fatigue properties of the injection molded polymers did not correlate with yield strength as would be traditionally observed in metals. Rather, the fatigue properties and the capacity to maintain properties with the introduction of surface porosity correlated with the fracture toughness of the polymers. Polymer structure impacted the materials relative capacity to maintain monotonic and cyclic properties in the face of surface texture and porosity. Generally, amorphous polymers with large ratios of upper to lower yield points demonstrated a more significant drop in ductility and fatigue strength with the introduction of porosity compared to crystalline polymers with smaller ratios in their upper to lower yield strength. The latter materials have more effective dissipation mechanisms to minimize the impact of surface porosity on both monotonic and cyclic damage. Copyright © 2016 Elsevier Ltd. All rights reserved.

Lunar Floor-Fractured Craters: Classification, Distribution and Implications for Magmatism and Shallow Crustal Structure

NASA Technical Reports Server (NTRS)

Jozwiak, L. M.; Head, J. W.; Neumann, G. A.; Zuber, M. T.; Smith, D. E.

2012-01-01

Floor-fractured craters (FFCs) are a class of lunar craters defined by their distinctly shallow, often plate-like floors, and combinations of radial, con-centric, and polygonal floor-fractures; a variety of other interior features are often observed, such as moats, ridges, small dark-haloed pits, and patches of mare material. They were first classified by Schultz [1] , who recognized eight overall types of floor-fractured crater. These eight subtypes have widely differing appearances, a factor that could provide insight into formation mechanisms (different manifestations of the same mechanism, or indicators of varying formation mechanisms). Two formation mechanisms for FFCs were initially proposed: 1) magmatic intrusion [1], in which magma rising toward the surface in dikes encountered low-density breccia lenses beneath crater floors and spread laterally to form sills, raising and fracturing the crater floor. 2) viscous relaxation [2], in which the properties of the crust permitted viscous flow in the vicinity of the crater, causing long-wavelength relaxation of the topography and uplift and fracturing of the crater floor. Critical to distinguishing between these two end-member hypotheses and identifying others is a quantitative assessment of the topography of FFCs and knowledge of their regional and local settings. The purpose of this study is to use newly available Lunar Reconnaissance Orbiter (LRO) Lunar Orbiter Laser Altimeter (LOLA) altimeter and Lunar Reconnaissance Orbiter Camera (LROC) image data to provide an updated global catalog of the locations, classes, morphometric and morphologic characteristics of all lunar floor-fractured craters. We use the excellent 8-class system initially described in Schultz [1] as a starting point for classification and the enhanced LOLA/LROC data sets to examine and categorize all FFCs; we found evidence for a new FFC class, discernably different from the previously existing types. Our approach, and the global categorization of all FFCs, permits the spatial distribution of each FFC-subtype to be plotted and assessed allowing for further investigation into FFC formation mechanisms. Upon completion, the data set will be made available on our web site at http://www.planetary.brown.edu/html_pages/data.htm.

Cratering in glasses impacted by debris or micrometeorites

NASA Technical Reports Server (NTRS)

Wiedlocher, David E.; Kinser, Donald L.

1993-01-01

Mechanical strength measurements on five glasses and one glass-ceramic exposed on LDEF revealed no damage exceeding experimental limits of error. The measurement technique subjected less than 5 percent of the sample surface area to stresses above 90 percent of the failure strength. Seven micrometeorite or space debris impacts occurred at locations which were not in that portion of the sample subjected to greater than 90 percent of the applied stress. As a result of this, the impact events on the sample were not detected in the mechanical strength measurements. The physical form and structure of the impact sites was carefully examined to determine the influence of those events upon stress concentration associated with the impact and the resulting mechanical strength. The size of the impact site, insofar as it determines flaw size for fracture purposes, was examined. Surface topography of the impacts reveals that six of the seven sites display impact melting. The classical melt crater structure is surrounded by a zone of fractured glass. Residual stresses arising from shock compression and from cooling of the fused zone cannot be included in the fracture mechanics analyses based on simple flaw size measurements. Strategies for refining estimates of mechanical strength degradation by impact events are presented.

A model for the origin of Martian polygonal terrain

NASA Technical Reports Server (NTRS)

Mcgill, G. E.

1993-01-01

Extensive areas of the Martian northern plains in Utopia and Acidalia Planitiae are characterized by 'polygonal terrain.' Polygonal terrain consists of material cut by complex troughs defining a pattern resembling mudcracks, columnar joints, or frost-wedge polygons on the Earth. However, the Martian polygons are orders of magnitude larger than these potential Earth analogs, leading to severe mechanical difficulties for genetic models based on simple analogy arguments. Stratigraphic studies show that the polygonally fractured material in Utopia Planitia was deposited on a land surface with significant topography, including scattered knobs and mesas, fragments of ancient crater rims, and fresh younger craters. Sediments or volcanics deposited over topographically irregular surfaces can experience differential compaction producing drape folds. Bending stresses due to these drape folds would be superposed on the pervasive tensile stresses due to desiccation or cooling, such that the probability of fracturing is enhanced above buried topographic highs and suppressed above buried topographic lows. Thus it was proposed that the scale of the Martian polygons is controlled by the spacing of topographic highs on the buried surface rather than by the physics of the shrinkage process.

Effect of Aperture Field Variability, Flow Rate, and Ionic Strength on Colloid Transport in Single Fractures: Laboratory-Scale Experiments and Numerical Simulation

NASA Astrophysics Data System (ADS)

Zheng, Q.; Dickson, S.; Guo, Y.

2007-12-01

A good understanding of the physico-chemical processes (i.e., advection, dispersion, attachment/detachment, straining, sedimentation etc.) governing colloid transport in fractured media is imperative in order to develop appropriate bioremediation and/or bioaugmentation strategies for contaminated fractured aquifers, form management plans for groundwater resources to prevent pathogen contamination, and identify suitable radioactive waste disposal sites. However, research in this field is still in its infancy due to the complex heterogeneous nature of fractured media and the resulting difficulty in characterizing this media. The goal of this research is to investigate the effects of aperture field variability, flow rate and ionic strength on colloid transport processes in well characterized single fractures. A combination of laboratory-scale experiments, numerical simulations, and imaging techniques were employed to achieve this goal. Transparent replicas were cast from natural rock fractures, and a light transmission technique was employed to measure their aperture fields directly. The surface properties of the synthetic fractures were characterized by measuring the zeta-potential under different ionic strengths. A 33 (3 increased to the power of 3) factorial experiment was implemented to investigate the influence of aperture field variability, flow rate, and ionic strength on different colloid transport processes in the laboratory-scale fractures, specifically dispersion and attachment/detachment. A fluorescent stain technique was employed to photograph the colloid transport processes, and an analytical solution to the one-dimensional transport equation was fit to the colloid breakthrough curves to calculate the average transport velocity, dispersion coefficient, and attachment/detachment coefficient. The Reynolds equation was solved to obtain the flow field in the measured aperture fields, and the random walk particle tracking technique was employed to model the colloid transport experiments. The images clearly show the development of preferential pathways for colloid transport in the different aperture fields and under different flow conditions. Additionally, a correlation between colloid deposition and fracture wall topography was identified. This presentation will demonstrate (1) differential transport between colloid and solute in single fractures, and the relationship between differential transport and aperture field statistics; (2) the relationship between the colloid dispersion coefficient and aperture field statistics; and (3) the relationship between attachment/detachment, aperture field statistics, fracture wall topography, flow rate, and ionic strength. In addition, this presentation will provide insight into the application of the random walk particle tracking technique for modeling colloid transport in variable-aperture fractures.

The origin of channels and associated deposits in the Elysium region of Mars

NASA Technical Reports Server (NTRS)

Christiansen, Eric H.; Hoppin, Richard A.

1987-01-01

Photogeological studies of the Elysium volcanic province of Mars show that its sinuous channels are part of a large deposit which probably was emplaced as a series of huge volcanic debris flows or lahars. The suggestion is based on evidence that the lahars were : (1) gravity-driven mass flow deposits (lobate outlines, steep snouts, smooth medial channels and rough lateral deposits--the deposits narrow and widen in accord with topography, and they extend downslope); (2) wet (channeled surfaces, drainage features); and (3) associated with volcanism (the deposits and channels extend from a system of fractures which fed lava flows). It is conceivable that heat associated with magmatism melted ground ice below the Elysium volcanoes, formed a muddy slurry which issued out of regional fractures and spread over the adjoining plain.

Regional flow in the Baltic Shield during Holocene coastal regression

USGS Publications Warehouse

Voss, Clifford I.; Andersson, Johan

1993-01-01

The occurrence of saline waters in the Baltic Shield in Sweden is consistent with ongoing but incomplete Holocene flushing and depends on the geometry and connectivity of conductive structures at both regional and local scales, and on the surface topography. Numerical simulation of regional variable-density fluid flow during Holocene land-rise and coastal regression shows that the existence of any old saline water, whether derived from submarine recharge in regions below Sweden's highest postglacial coastline or geochemical processes in the crystalline rock, is an indication either of slow fluid movements through the bedrock over long times, or of long travel distances through fracture systems before arriving at measurement points. During the land-rise period, regional flow is not affected by the variable density of fluids in the upper few kilometers of the shield, and the topography of the water table is the only driving force. The spatial distribution of meteoric flushing water and pre-Holocene waters may be complex, with the possibility of relatively fresh water in fracture zones below salty units even at depths of a few kilometers. The domination of the topographic driving force implies that deep saline water is not necessarily stagnant, and significant flow may be expected to occur in well-connected horizons even at depth. Local topography variation and fracture zone location combine to create a complex flow field in which local topographic driving forces extend to considerable depth in some areas, whereas regional topographic forces predominate in others. Thus, a pattern may be difficult to discern in measurements of the regional salinity distribution, although it is clear that the coastal region is the major zone of discharge for deeper pre-Holocene fluids. During the land-rise period, the regional flow field equilibrates with changing climatic conditions and coastal positions, while the distribution of flushing water and older water lags and will perpetually change between successive glaciations. These characteristics have direct implications for the safety of nuclear water repositories located at depth in Baltic Shield rocks.

A brief discussion about image quality and SEM methods for quantitative fractography of polymer composites.

PubMed

Hein, L R O; Campos, K A; Caltabiano, P C R O; Kostov, K G

2013-01-01

The methodology for fracture analysis of polymeric composites with scanning electron microscopes (SEM) is still under discussion. Many authors prefer to use sputter coating with a conductive material instead of applying low-voltage (LV) or variable-pressure (VP) methods, which preserves the original surfaces. The present work examines the effects of sputter coating with 25 nm of gold on the topography of carbon-epoxy composites fracture surfaces, using an atomic force microscope. Also, the influence of SEM imaging parameters on fractal measurements is evaluated for the VP-SEM and LV-SEM methods. It was observed that topographic measurements were not significantly affected by the gold coating at tested scale. Moreover, changes on SEM setup leads to nonlinear outcome on texture parameters, such as fractal dimension and entropy values. For VP-SEM or LV-SEM, fractal dimension and entropy values did not present any evident relation with image quality parameters, but the resolution must be optimized with imaging setup, accompanied by charge neutralization. © Wiley Periodicals, Inc.

Dawn at Ceres: A Synopsis

NASA Astrophysics Data System (ADS)

Russell, Christopher T.; Raymond, Carol A.; DeSanctis, Maria Christina; Nathues, Andreas; Prettyman, Thomas; Castillo-Rogez, Julie C.; McSween, Harry Y.; Pieters, Carle M.; Jaumann, Ralf; Buczkowski, Debra; Ammannito, Eleonora; Hiesinger, Harald; Toplis, Michael J.; Li, Jian-Yang; Park, Ryan S.

2017-04-01

Dawn has now been in orbit about Ceres for over two years. In that time, it has spiraled down to the lowest altitudes and back to the highest altitudes and on its way, performed global mapping of Ceres' surface morphology, topography, gravity, mineralogy, and elemental composition. It found a water-rich body with a temporary atmosphere that was sufficiently strong to deflect the solar wind. This atmosphere appears after the Sun produces high fluxes of very energetic protons. This time-varying association explains why 1-AU observations previously had both detected and failed to detect a water or OH atmosphere at Ceres. At global scale, the surface typically consists of a layer of phyllosilicates, including ammoniated clays, Ca-Mg carbonates and a dark but spectrally neutral component. At local scale, the Cerealia facula in Occator crater was found to be the largest known extraterrestrial accumulation of Na-carbonates. The Ernutet crater was peppered with organic molecules, possibly of internal origin, while small km square-sized regions of exposed ice were found in several places on the surface. In broad regions at high latitude, ice is just beneath the surface, and the depth to the ice table varies with latitude. Fractured crater floors suggesting stresses produced by uplift of sub-surface material were found, and the dome in the center of Occator craters' central pit was also postulated to be fractured by localized upwelling material. Ahuna mons, a 4-km high isolated mountain, further indicates the recent occurrence of cryovolcanic activity likely driven by brines. The gravity and topography data and the crater-size frequency distribution have been interpreted in terms of a rigid ice-rock shell covering a less rigid interior. Elemental data are consistent with ice-rock fractionation. The data clearly demonstrate that Ceres is a small exotic water-rich world, deserving of much attention in the next wave of planetary exploration.

Application of Unmanned Aerial System-based Photogrammetry to Monitor Landforms Evolution of Mudstone Badlands

NASA Astrophysics Data System (ADS)

Chen, Yichin

2017-04-01

Mudstone badlands are the area characteristized by its rapid erosion and steep, fractured, and barren landforms. Monitoring the topography changes in badland help improve our knowledge of the hillslope and river processing on landforms and develop susceptibility model for surface erosion hazards. Recently, advances in unmanned aerial system (UAS) and close-range photogrammetry technology have opened up the possibility of effectively measuring topography changes with high spatiotemporal resolutions. In this study, we used the UAS and close-range photogrammetry technology to monitor the topography changes in a rapidly eroded badland, south-western Taiwan. A small mudstone hillslope with area of 0.2 ha approximately and with slope gradient of 37 degrees was selected as the study site. A widely used and commercial quadcopter equipped non-metric camera was used to take images with ground sampling distance (GSD) 5 mm approximately. The Pix4DMapper, a commercial close-range photogrammetry software, was used to perform stereo matching, extract point clouds, generate digital surface models (DSMs) and orthoimage. To control model accuracy, a set of ground control points was surveyed by using eGPS. The monitoring was carried out after every significant rainfall event that may induced observable erosion in the badland site. The results show that DSMs have the GSDs of 4.0 5.4 mm and vertical accuracy of 61 116 mm. The accuracy largely depends on the quality of ground control points. The spatial averaged erosion rate during six months of monitoring was 328 mm, which is higher in the gully sides than in the ridges. The erosion rate is positively correlated with the slope gradient and drainage contributing area that implies the important role of surface gully erosion in mudstone badland erosion. This study shows that UAS and close-range photogrammetry technology can be used to monitor the topography change in badland areas effectively and can provide high spatiotemporal resolutions of DSMs for developing distributed surface erosion models.

The topography of Ceres and implications for the formation of linear surface structures

NASA Astrophysics Data System (ADS)

Buczkowski, D.; Otto, K.; Ruesch, O.; Scully, J. E. C.; Williams, D. A.; Mest, S. C.; Schenk, P.; Jaumann, R.; Nathues, A.; Preusker, F.; Park, R. S.; Raymond, C. A.; Russell, C. T.

2015-12-01

NASA's Dawn spacecraft began orbiting the dwarf planet Ceres in April 2015. Framing Camera data from the Approach (1.3 km/px) and Survey (415 m/px) orbits include digital terrain models derived from processing stereo images. These models have supported various scientific studies of the surface. The eastern hemisphere of Ceres is topographically higher than the western hemisphere. Some of linear structures on Ceres (which include grooves, pit crater chains, fractures and troughs) appear to be radial to the large basins Urvara and Yalode, and most likely formed due to impact processes. However, set of regional linear structures (RLS) that do not have any obvious relationship to impact craters are found on the eastern hemisphere topographic high region. Many of the longer RLS are comprised of smaller structures that have linked together, suggestive of en echelon fractures. Polygonal craters, theorized to form when pervasive subsurface fracturing affects crater formation [1], are widespread on Ceres [2], and those proximal to the RLS have straight crater rims aligned with the grooves and troughs, suggesting that the RLS are fracture systems. A cross-section of one RLS is displayed in FC images of the Occator crater wall. Comparing these images to the digital terrain models show 1) that the structure dips ~60º and 2) there is downward motion on the hanging wall, implying normal faulting. The digital terrain models also reveal the presence of numerous positive relief features with sub-circular shapes. These dome-like features have been tentatively interpreted as volcanic/magmatic features [3]; other possibilities include salt domes. Analog models of domal uplift in areas of regional extension [4] predict patterns of linear structures similar to those observed in the RLS near Occator. Utilizing topography data provided by the Ceres digital terrain models, we assess the relationship between the RLS and nearby domes and topographic high regions to determine the mechanism by which the RLS may have formed. [1] Thomas, P.C. et al. (1999) Icarus, doi: 10.1006/icar.1999.6121 [2] Otto et al. (2015) EPSC2015-284 [3] Ruesch et al. [this meeting] [4] Sims et al. (2013) AAPG Bulletin, doi: 10.1306/02101209136

Lithospheric Subduction on Earth and Venus?

NASA Astrophysics Data System (ADS)

Sandwell, D. T.; Garcia, E.; Stegman, D. R.; Schubert, G.

2016-12-01

There are three mechanisms by which terrestrial planets can shed excess heat: conduction across a surface thermal boundary layer; advection of heat through volcanic pipes; and mobile plates/subduction. On the Earth about 30% is released by conduction and 70% by subduction. The dominant mode of heat transport on Venus is largely unknown. Plate flexure models rule out significant heat loss by conduction and the resurfacing from active volcanism is in discordance with a surface age of 600 Ma. There are 9000 km of trenches on Venus that may have been subduction sites but they do not appear active today and are only 25% of the length of the subduction zones on the Earth. Turcotte and others have proposed an episodic recycling model that has short bursts ( 150 Ma) of plate tectonic activity followed by long periods ( 450 Ma) of stagnant lid convection. This talk will review the arguments for and against subduction zones on Venus and discuss possible new satellite observations that could help resolve the subduction issue. Figure Caption. (a) Global mosaic of Magellan SAR imagery. (b) Zoom of area along the Artemis trench, which has similar topography and fracture patterns as the Aleutian subduction zone on Earth. Trench and outer rise lines were digitized from the matching topography image (not shown). The Magellan SAR imagery and topography, displayed on Google Earth, can be downloaded at http://topex.ucsd.edu/venus/index.html

Colloid transport in model fracture filling materials

NASA Astrophysics Data System (ADS)

Wold, S.; Garcia-Garcia, S.; Jonsson, M.

2010-12-01

Colloid transport in model fracture filling materials Susanna Wold*, Sandra García-García and Mats Jonsson KTH Chemical Science and Engineering Royal Institute of Technology, SE-100 44 Stockholm, Sweden *Corresponding author: E-mail: wold@kth.se Phone: +46 8 790 6295 In colloid transport in water-bearing fractures, the retardation depends on interactions with the fracture surface by sorption or filtration. These mechanisms are difficult to separate. A rougher surface will give a larger area available for sorption, and also when a particle is physically hindered, it approaches the surface and enables further sorption. Sorption can be explained by electrostatics were the strongest sorption on minerals always is observed at pH below pHpzc (Filby et al., 2008). The adhesion of colloids to mineral surfaces is related to the surface roughness according to a recent study (Darbha et al., 2010). There is a large variation in the characteristics of water-bearing fractures in bedrock in terms of aperture distribution, flow velocity, surface roughness, mineral distributions, presence of fracture filling material, and biological and organic material, which is hard to implement in modeling. The aim of this work was to study the transport of negatively charged colloids in model fracture filling material in relation to flow, porosity, mineral type, colloid size, and surface charge distribution. In addition, the impact on transport of colloids of mixing model fracture filling materials with different retention and immobilization capacities, determined by batch sorption experiments, was investigated. The transport of Na-montmorillonite colloids and well-defined negatively charged latex microspheres of 50, 100, and 200 nm diameter were studied in either columns containing quartz or quartz mixed with biotite. The ionic strength in the solution was exclusively 0.001 and pH 6 or 8.5. The flow rates used were 0.002, 0.03, and 0.6 mL min-1. Sorption of the colloids on the model fracture minerals was studied prior to the transport experiments under the same conditions. By varying the amount of solid substrate, it was possible to determine an interaction constant from a linear expression. Complementary zeta potential measurements and scanning electron microscopy (SEM) imaging were performed to examine the mineral surfaces after exposure to colloids. In experiments with low flow rates the retention of the colloids in the transport experiments were attributed to the interaction constants including both physical filtration and sorption. At higher flow rate the interactions between colloids and mineral surfaces were also significant but not as pronounced. Immobilization and retardation of the colloids were reflected by the interaction constants, which included both an irreversible and a reversible component of physical filtration and sorption. References Darbha, G.K., Schaefer, T., Heberling, F., Lüttge, A. and Fisher, C. 2010. Retention of Latex Colloids on Calcite as a Function of Surface Roughness and Topography. Langmuir, 26(7), 4743-4752. Filby, A., Plaschke, M., Geckeis, H., Fanghänel, Th. 2008. Interaction of latex colloids with mineral surfaces and Grimsel granodiorite. J. Contam. Hydrol., 102, 273-284.

Pathomorphism of spiral tibial fractures in computed tomography imaging.

PubMed

Guzik, Grzegorz

2011-01-01

Spiral fractures of the tibia are virtually homogeneous with regard to their pathomorphism. The differences that are seen concern the level of fracture of the fibula, and, to a lesser extent, the level of fracture of the tibia, the length of fracture cleft, and limb shortening following the trauma. While conventional radiographs provide sufficient information about the pathomorphism of fractures, computed tomography can be useful in demonstrating the spatial arrangement of bone fragments and topography of soft tissues surrounding the fracture site. Multiple cross-sectional computed tomography views of spiral fractures of the tibia show the details of the alignment of bone chips at the fracture site, axis of the tibial fracture cleft, and topography of soft tissues that are not visible on standard radiographs. A model of a spiral tibial fracture reveals periosteal stretching with increasing spiral and longitudinal displacement. The cleft in tibial fractures has a spiral shape and its line is invariable. Every spiral fracture of both crural bones results in extensive damage to the periosteum and may damage bellies of the long flexor muscle of toes, flexor hallucis longus as well as the posterior tibial muscle. Computed tomography images of spiral fractures of the tibia show details of damage that are otherwise invisible on standard radiographs. Moreover, CT images provide useful information about the spatial location of the bone chips as well as possible threats to soft tissues that surround the fracture site. Every spiral fracture of the tibia is associated with disruption of the periosteum. 1. Computed tomography images of spiral fractures of the tibia show details of damage otherwise invisible on standard radiographs, 2. The sharp end of the distal tibial chip can damage the tibialis posterior muscle, long flexor muscles of the toes and the flexor hallucis longus, 3. Every spiral fracture of the tibia is associated with disruption of the periosteum.

Mola Topography Supports Drape-Folding Models for Polygonal Terrain of Utopia Planitia, Mars

NASA Technical Reports Server (NTRS)

McGill, George E.; Buczkowski, D. L.

2002-01-01

One of the most important questions we ask about Mars is whether or not there have ever been large bodies of standing water on the surface. The polygonal terrains of Utopia and Acidalia Planitiae are located in the lowest parts of the northern lowlands, the most logical places for water to pond and sediments to accumulate. Showing that polygonal terrain is sedimentary in origin would represent strong evidence in favor of a northern ocean. A number of hypotheses for the origin of the giant martian polygons have been proposed, from the cooling of lava to frost wedging to the desiccation of wet sediments, but Pechman showed that none of these familiar processes could be scaled up to martian dimensions. Two models for polygon origin attempt to explain the scale of the martian polygons by postulating drape folding of a cover material, either sedimentary or volcanic, over an uneven, buried surface. The drape folding would produce bending stresses in the surface layers that increase the probability of Fracturing over drape anticlines and suppress the probability of fracturing over drape synclines. However, both models require an additional source of extensional strain to produce the total strain needed to produce the observed troughs.

Failure analysis of ceramic clinical cases using qualitative fractography.

PubMed

Scherrer, Susanne S; Quinn, Janet B; Quinn, George D; Kelly, J Robert

2006-01-01

To educate dental academic staff and clinicians on the application of descriptive (qualitative) fractography for analyses of clinical and laboratory failures of brittle materials such as glass and ceramic. The fracture surface topography of failed glass, glass fiber-reinforced composite, and ceramic restorations (Procera, Cerestore, In-Ceram, porcelain-fused-to-metal) was examined utilizing a scanning electron microscope. Replicas and original failed parts were scrutinized for classic fractographic features such as hackle, wake hackle, twist hackle, arrest lines, and mirrors. Failed surfaces of the veneering porcelain of ceramic and porcelain-fused-to-metal crowns exhibited hackle, wake hackle, twist hackle, arrest lines, and compression curl, which were produced by the interaction of the advancing crack with the microstructure of the material. Fracture surfaces of glass and glass fiber-reinforced composite showed additional features, such as velocity hackle and mirrors. The observed features were good indicators of the local direction of crack propagation and were used to trace the crack back to an initial starting area (the origin). Examples of failure analysis in this study are intended to guide the researcher in using qualitative (descriptive) fractography as a tool for understanding the failure process in brittle restorative materials and also for assessing possible design inadequacies.

Effect of core ceramic grinding on fracture behaviour of bilayered lithium disilicate glass-ceramic under two loading schemes.

PubMed

Wang, Xiao-Dong; Jian, Yu-Tao; Guess, Petra C; Swain, Michael V; Zhang, Xin-Ping; Zhao, Ke

2014-11-01

The purpose of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered lithium disilicate glass-ceramic (LDG) under two loading schemes. Interfacial surfaces of sandblasted LDG disks (A) were ground with 220 (B), 500 (C) and 1200 (D) grit silicon carbide (SiC) sandpapers, respectively. Surface roughness and topographic analysis were performed using a profilometer and a scanning electron microscopy (SEM), and then underwent retesting after veneer firing. Biaxial fracture strength (σf) and Weibull modulus (m) were calculated either with core in tension (subgroup t) or in compression (subgroup c). Failure modes were observed by SEM, and loading induced stress distribution was simulated and analyzed by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis, one-way ANOVA, and paired test at a significance level of 0.05. As the grits size of SiC increased, LDG surface roughness decreased from group A to D (p<0.001), which remained unchanged after veneer firing. No difference in σf (p=0.41 for subgroups At-Dt; p=0.11 for subgroups Ac-Dc), m values as well as failure modes was found among four subgroups for both loading schemes. Specimens in subgroup t showed higher σf (p<0.001) and m values than subgroup c. Stress distribution between loading schemes did not differ from each other. Cracks, as the dominant failure mode initiated from bottom tensile surface. No sign of interfacial cracking or delamination was observed for all groups. Technician grinding changed surface topography of LDG ceramic material, but was not detrimental to the bilayered system strength after veneer application. LDG bilayered system was more sensitive to fracture when loaded with veneer porcelain in tension. Within the limitations of the simulated grinding applied, it is concluded that veneer porcelain can be applied directly after technician grinding of LDG ceramic as it has no detrimental effect on the strength of bilayered structures. The connector areas of LDG fixed dental prosthesis are more sensitive to fracture compared with single crowns, and should be fabricated with more caution. Copyright © 2014 Elsevier Ltd. All rights reserved.

Damage mechanisms in bithermal and thermomechanical fatigue of Haynes 188

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Halford, Gary R.

1992-01-01

Post failure fractographic and metallographic studies were conducted on Haynes 188 specimens fatigued under bithermal and thermomechanical loading conditions between 316 and 760 C. Bithermal fatigue specimens examined included those tested under high strain rate in-phase and out-phase, tensile creep in-phase, and compressive creep out-of-phase loading conditions. Specimens tested under in-phase and out-of-phase thermomechanical fatigue were also examined. The nature of failure mode (transgrandular versus intergranular), the topography of the fracture surface, and the roles of oxidation and metallurgical changes were studied for each type of bithermal and thermomechanical test.

TOPOGRAPHY, STRESSES, AND STABILITY AT YUCCA MOUNTAIN, NEVADA.

USGS Publications Warehouse

Wolfs, Henri; Savage, William Z.

1985-01-01

Plane-strain solutions are used to analyze the influence of topography on the state of stress at Yucca Mountain, Nye County, Nevada. The results are in good agreement with the measured stress components obtained in drill holes by the hydraulic-fracturing technique, particularly those measured directly beneath the crest of the ridge, and indicate that these stresses are gravitationally induced. A separate analysis takes advantage of the fact that a well-developed set of vertical faults and fractures, subparallel to the ridge trend, imparts a vertical transverse isotropy to the rock and that, as a consequence of gravitational loading, unequal horizontal stresses are induced in directions perpendicular and parallel to the anisotropy.

Feedbacks Between Topographic Stress and Drainage Basin Evolution

NASA Astrophysics Data System (ADS)

Perron, J.; Martel, S. J.; Singha, K.; Slim, M. I.

2013-12-01

Theoretical calculations imply that stresses produced by gravity acting on topography may be large enough in some scenarios to fracture rock. Predicted stress fields beneath ridges and valleys can differ dramatically, which has led several authors to hypothesize feedbacks between topographic stress, rock fracture and landscape evolution. However, there have been few attempts to explore these feedbacks. We use a coupled model to identify possible feedbacks between topographic stress and drainage basin evolution. The domain is a cross-section of a valley consisting of a bedrock channel and adjacent soil-mantled hillslopes. The bedrock surface evolves due to channel incision, soil production, and rock uplift, and soil thickness evolves due to soil production and transport. Plane stresses at and below the bedrock surface are calculated with a boundary element method that accounts for both ambient tectonic stress and topographic stress. We assume that the stress field experienced by rock as it is exhumed influences the likelihood that it will develop fractures, which make the rock more susceptible to weathering, disaggregation and erosion. A measure of susceptibility to shear fracture, the most likely failure mode under regional compression, serves as a proxy for rock damage. We couple the landscape evolution model to the stress model by assuming that rock damage accelerates the rates of soil production and channel incision, with two endmember cases: rates scale with the magnitude of the damage proxy at the bedrock surface, or with cumulative damage acquired during rock exhumation. The stress-induced variations in soil production and channel incision alter the soil thickness and topography, which in turn alter the stress field. Comparing model simulations with and without these feedbacks, we note several predicted consequences of topographic stress for drainage basin evolution. Rock damage is typically focused at or near the foot of hillslopes, which creates thicker soils near the valley bottom than near the ridgetop. This gradient in soil thickness is largest, and the thickest soil furthest downslope, if most rock damage is assumed to occur near the surface. Ambient tectonic stress also has a strong effect on hillslopes, with more compressive horizontal stress steepening the soil thickness gradient and displacing the thickest soil farther downslope. Rock damage in the valley bottom scales with valley depth, creating a positive feedback between relief and channel incision. This produces higher relief during transient channel incision, but steady-state relief is insensitive to stress effects because the positive feedback is limited by reduction of the channel slope. However, the fact that valleys are typically deepest in the middle of a drainage basin implies that channel profiles will be more concave if stresses enhance channel incision. Observational tests of these qualitative predictions will help evaluate the significance of suspected feedbacks between topographic stress and landscape evolution.

Observations on the Role of Hydrogen in Facet Formation in Near-alpha Titanium (Preprint)

DTIC Science & Technology

2011-05-01

using quantitative tilt fractography and electron backscatter diffraction while facet topography was examined using ultra high resolution scanning...quantitative tilt fractography and electron backscatter diffraction while facet topography was examined using ultra high resolution scanning electron...tilt fractography / electron backscatter diffraction (EBSD) technique in which both the crystallographic orientation of the fractured grain and the

Ambient vibrations of unstable rock slopes - insights from numerical modeling

NASA Astrophysics Data System (ADS)

Burjanek, Jan; Kleinbrod, Ulrike; Fäh, Donat

2017-04-01

The recent events in Nepal (2015 M7.8 Gorkha) and New Zealand (2016 M7.8 Kaikoura) highlighted the importance of earthquake-induced landslides, which caused significant damages. Moreover, landslide created dams present a potential developing hazard. In order to reduce the costly consequences of such events it is important to detect and characterize earthquake susceptible rock slope instabilities before an event, and to take mitigation measures. For the characterisation of instable slopes, acquisition of ambient vibrations might be a new alternative to the already existing methods. We present both observations and 3D numerical simulations of the ambient vibrations of unstable slopes. In particular, models of representative real sites have been developed based on detailed terrain mapping and used for the comparison between synthetics and observations. A finite-difference code has been adopted for the seismic wave propagation in a 3D inhomogeneous visco-elastic media with irregular free surface. It utilizes a curvilinear grid for a precise modeling of curved topography and local mesh refinement to make computational mesh finer near the free surface. Topographic site effects, controlled merely by the shape of the topography, do not explain the observed seismic response. In contrast, steeply-dipping compliant fractures have been found to play a key role in fitting observations. Notably, the synthetized response is controlled by inertial mass of the unstable rock, and by stiffness, depth and network density of the fractures. The developed models fit observed extreme amplification levels (factors of 70!) and show directionality as well. This represents a possibility to characterize slope structure and infer depth or volume of the slope instability from the ambient noise recordings in the future.

Understanding the mechanisms of solid-water reactions through analysis of surface topography.

PubMed

Bandstra, Joel Z; Brantley, Susan L

2015-12-01

The topography of a reactive surface contains information about the reactions that form or modify the surface and, therefore, it should be possible to characterize reactivity using topography parameters such as surface area, roughness, or fractal dimension. As a test of this idea, we consider a two-dimensional (2D) lattice model for crystal dissolution and examine a suite of topography parameters to determine which may be useful for predicting rates and mechanisms of dissolution. The model is based on the assumption that the reactivity of a surface site decreases with the number of nearest neighbors. We show that the steady-state surface topography in our model system is a function of, at most, two variables: the ratio of the rate of loss of sites with two neighbors versus three neighbors (d(2)/d(3)) and the ratio of the rate of loss of sites with one neighbor versus three neighbors (d(1)/d(3)). This means that relative rates can be determined from two parameters characterizing the topography of a surface provided that the two parameters are independent of one another. It also means that absolute rates cannot be determined from measurements of surface topography alone. To identify independent sets of topography parameters, we simulated surfaces from a broad range of d(1)/d(3) and d(2)/d(3) and computed a suite of common topography parameters for each surface. Our results indicate that the fractal dimension D and the average spacing between steps, E[s], can serve to uniquely determine d(1)/d(3) and d(2)/d(3) provided that sufficiently strong correlations exist between the steps. Sufficiently strong correlations exist in our model system when D>1.5 (which corresponds to D>2.5 for real 3D reactive surfaces). When steps are uncorrelated, surface topography becomes independent of step retreat rate and D is equal to 1.5. Under these conditions, measures of surface topography are not independent and any single topography parameter contains all of the available mechanistic information about the surface. Our results also indicate that root-mean-square roughness cannot be used to reliably characterize the surface topography of fractal surfaces because it is an inherently noisy parameter for such surfaces with the scale of the noise being independent of length scale.

Geophysical models for the formation and evolution of coronae on Venus

NASA Technical Reports Server (NTRS)

Janes, Daniel M.; Squyres, Steven W.; Bindschadler, Duane L.; Baer, Gidon; Schubert, Gerald; Sharpton, Virgil L.; Stofan, Ellen R.

1992-01-01

The proposition that Venusian coronae form over sites of mantle upwelling and are modified by subsequent gravitational relaxation is examined using two geophysical models to determine whether and under what conditions these mechanisms can produce the topography and tectonics exhibited by coronae in the Magellan altimetry data and radar images. It is shown that mantle diapirism can produce the domical topography of novae, which may be coronae in the earliest stage of formation. The model stresses induced at the surface by a mantle diapir imply the formation of radially oriented extensional fracturing as observed in novae. The novae dimensions indicate that the diapirs responsible for them are smaller than about 100 km in radius and that the elastic lithosphere is less than 32 km thick. A flattened diapir at the top of the mantle is modeled and shown to result in plateaulike uplift. The volume of the flattened model diapir is similar to that of the spherical diapirs derived for novae.

Origin of bending in uncoated microcantilever - Surface topography?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lakshmoji, K.; Prabakar, K.; Tripura Sundari, S., E-mail: sundari@igcar.gov.in

2014-01-27

We provide direct experimental evidence to show that difference in surface topography on opposite sides of an uncoated microcantilever induces bending, upon exposure to water molecules. Examination on opposite sides of the microcantilever by atomic force microscopy reveals the presence of localized surface features on one side, which renders the induced stress non-uniform. Further, the root mean square inclination angle characterizing the surface topography shows a difference of 73° between the opposite sides. The absence of deflection in another uncoated microcantilever having similar surface topography confirms that in former microcantilever bending is indeed induced by differences in surface topography.

Time-domain full-waveform inversion of Rayleigh and Love waves in presence of free-surface topography

NASA Astrophysics Data System (ADS)

Pan, Yudi; Gao, Lingli; Bohlen, Thomas

2018-05-01

Correct estimation of near-surface seismic-wave velocity when encountering lateral heterogeneity and free surface topography is one of the challenges to current shallow seismic. We propose to use time-domain full-waveform inversion (FWI) of surface waves, including both Rayleigh and Love waves, to solve this problem. We adopt a 2D time-domain finite-difference method with an improved vacuum formulation (IVF) to simulate shallow-seismic Rayleigh wave in presence of free-surface topography. We modify the IVF for SH-wave equation for the simulation of Love wave in presence of topographic free surface and prove its accuracy by benchmark tests. Checkboard model tests are performed in both cases when free-surface topography is included or neglected in FWI. Synthetic model containing a dipping planar free surface and lateral heterogeneity was then tested, in both cases of considering and neglecting free-surface topography. Both checkerboard and synthetic models show that Rayleigh- and Love-wave FWI have similar ability of reconstructing near-surface structures when free-surface topography is considered, while Love-wave FWI could reconstruct near-surface structures better than Rayleigh-wave when free-surface topography is neglected.

RhoA-Mediated Functions in C3H10T1/2 Osteoprogenitors Are Substrate Topography Dependent.

PubMed

Ogino, Yoichiro; Liang, Ruiwei; Mendonça, Daniela B S; Mendonça, Gustavo; Nagasawa, Masako; Koyano, Kiyoshi; Cooper, Lyndon F

2016-03-01

Surface topography broadly influences cellular responses. Adherent cell activities are regulated, in part, by RhoA, a member of the Rho-family of GTPases. In this study, we evaluated the influence of surface topography on RhoA activity and associated cellular functions. The murine mesenchymal stem cell line C3H10T1/2 cells (osteoprogenitor cells) were cultured on titanium substrates with smooth topography (S), microtopography (M), and nanotopography (N) to evaluate the effect of surface topography on RhoA-mediated functions (cell spreading, adhesion, migration, and osteogenic differentiation). The influence of RhoA activity in the context of surface topography was also elucidated using RhoA pharmacologic inhibitor. Following adhesion, M and N adherent cells developed multiple projections, while S adherent cells had flattened and widespread morphology. RhoA inhibitor induced remarkable longer and thinner cytoplasmic projections on all surfaces. Cell adhesion and osteogenic differentiation was topography dependent with S < M and N surfaces. RhoA inhibition increased adhesion on S and M surfaces, but not N surfaces. Cell migration in a wound healing assay was greater on S versus M versus N surfaces and RhoA inhibitor increased S adherent cell migration, but not N adherent cell migration. RhoA inhibitor enhanced osteogenic differentiation in S adherent cells, but not M or N adherent cells. RhoA activity was surface topography roughness dependent (S < M, N). RhoA activity and -mediated functions are influenced by surface topography. Smooth surface adherent cells appear highly sensitive to RhoA function, while nano-scale topography adherent cell may utilize alternative cellular signaling pathway(s) to influence adherent cellular functions regardless of RhoA activity. © 2015 Wiley Periodicals, Inc.

Implications of horsts and grabens on the development of canyons and seismicity on the west africa coast

NASA Astrophysics Data System (ADS)

Ola, Peter S.; Olabode, Solomon O.

2018-04-01

Subsurface basement topography in the Nigerian portion of the Benin Basin has been studied using borehole data of wells drilled to the basement and one strike line of seismic section. Two areas of a sharp drop in topography with a horst in between were observed in the study area. These features were projected to a seismic section in the offshore area of the Benin basin. The result depicts the structural features as horst and grabens coinciding with the Avon platform bounded on the right side by Ise graben, and the Orimedu graben to the left. The observed relationship of the grabens with the present day location of Avon Canyon on the seismic section also suggests an active subsidence along fractured zones. The subsidence, which probably is occurring along similar fracture zones in the Gulf of Guinea, could be responsible for the occasionally reported seismicity on the margin of West Africa. A detailed seismographic study of the fracture zones is recommended.

Ground motion amplification at rock sites: the competing role of topography and fractured rocks in the San Giovanni fault, central Italy

NASA Astrophysics Data System (ADS)

Pischiutta, M.; Cara, F.; Di Giulio, G.; Vassallo, M.; Cultrera, G.

2017-12-01

Amplification at rock sites in areas of high topographic relief has been increasingly observed in the last years, with unexpected level of damage after strong earthquakes. In regions affected by recent tectonic activity, topographic irregularities can include fault damage zones. In such conditions, seismic waves can be locally amplified as a double effect of wave focusing along the topography and /or the presence of fractures/joints or locally weakened rocks. The role of topography vs. geological complexities in controlling the ground motion amplification at rock sites is a newly debated issue in the seismological community. The most crucial questions regard what is the real contribution of the topography shape and fracturing, and how to parameterize such effects for their inclusion in the seismic design codes. In this framework, the EMERSITO INGV task force installed 7 seismic stations across the San Giovanni fault, after the Amatrice mainshock of the 2016 sequence in Central Italy. This active normal fault is located in the area of the Montereale intermountain basin (Abruzzi region, Italy) and bounds the southwestern slope of Mt. Mozzano, a roughly 2D-shaped, up to 1450 m high pronounced topography. Moreover, this fault has been recently studied by several authors who performed detailed geological and geophysical surveys. Our stations recorded more than 100 earthquakes with magnitude ranging from 2.5 to 3.9 as well as a 4.4 M earthquake with hypocenter in Capitignano district, few kilometres far. We have analyzed in detail the recorded signals calculating the traditional spectral ratios at single station (HVSRs) and using the reference site (SSRs) using both ambient noise and earthquakes. In order to obtain a robust estimate of the site amplification effect at each station, we have investigated the influence of backazimuth and epicentral distance. We have also applied the time-domain covariance matrix analysis and the frequency domain polarization analysis. We have found that, in spite of the complexity of the seismic data, the observed polarization pattern is generally oriented orthogonal to the ridge elongation, as well as to the fault strike, suggesting the existence of a high angle relation between ground motion polarization and fracture systems.

Background research in support of the new grant proposal: Research consortium for X-ray topography on line X-19 at NSLS

NASA Astrophysics Data System (ADS)

Bilello, J. C.

1983-11-01

The status of the construction and installation of components of the synchrotron topography station is reported as well as progress in the development of hardware for interfacing and software for interactively controlling the 13 motors which automate the facility. Research focuses on the problem of X-ray optics and on techniques for applying topography to materials science. There is colaboration with other researchers in studying the nature of brittle fracture of refractory metals and in interpreting contact in the vicinity of crack tips.

Surface Topography Hinders Bacterial Surface Motility.

PubMed

Chang, Yow-Ren; Weeks, Eric R; Ducker, William A

2018-03-21

We demonstrate that the surface motility of the bacterium, Pseudomonas aeruginosa, is hindered by a crystalline hemispherical topography with wavelength in the range of 2-8 μm. The motility was determined by the analysis of time-lapse microscopy images of cells in a flowing growth medium maintained at 37 °C. The net displacement of bacteria over 5 min is much lower on surfaces containing 2-8 μm hemispheres than on flat topography, but displacement on the 1 μm hemispheres is not lower. That is, there is a threshold between 1 and 2 μm for response to the topography. Cells on the 4 μm hemispheres were more likely to travel parallel to the local crystal axis than in other directions. Cells on the 8 μm topography were less likely to travel across the crowns of the hemispheres and were also more likely to make 30°-50° turns than on flat surfaces. These results show that surface topography can act as a significant barrier to surface motility and may therefore hinder surface exploration by bacteria. Because surface exploration can be a part of the process whereby bacteria form colonies and seek nutrients, these results help to elucidate the mechanism by which surface topography hinders biofilm formation.

Effect of irradiation-induced plastic flow localization on ductile crack resistance behavior of a 9%Cr tempered martensitic steel

NASA Astrophysics Data System (ADS)

Chaouadi, R.

2008-01-01

This paper examines the effect of irradiation-induced plastic flow localization on the crack resistance behavior. Tensile and crack resistance measurements were performed on Eurofer-97 that was irradiated at 300 °C to neutron doses ranging between 0.3 and 2.1 dpa. A severe degradation of crack resistance behavior is experimentally established at quasi-static loading, in contradiction with the Charpy impact data and the dynamic crack resistance measurements. This degradation is attributed to the dislocation channel deformation phenomenon. At quasi-static loading rate, scanning electron microscopy observations of the fracture surfaces revealed a significant change of fracture topography, mainly from equiaxed dimples (mode I) to shear dimples (mode I + II). With increasing loading rate, the high peak stresses that develop inside the process zone activate much more dislocation sources resulting in a higher density of cross cutting dislocation channels and therefore an almost unaffected crack resistance. These explanations provide a rational to all experimental observations.

Origin of the Martian global dichotomy by crustal thinning in the late Noachian or early Hesperian

NASA Technical Reports Server (NTRS)

Mcgill, George E.; Dimitriou, Andrew M.

1990-01-01

The marked dichotomy in topography, surface age, and crustal thickness between the northern lowland (NL) and southern upland of Mars has been explained as due to an initially inhomogeneous crust, a single megaimpact event, several overlapping large basin impacts, and first-order convective overtum of the Martian mantle. All of these hypotheses propose that the dichotomy was formed before the end of the primordial heavy bombardment. Geological data indicate episodes of fracturing and faulting in the late Noachian and the early Hesperian, within the NL and along the lowland/highland boundary. Igneous activity also peaked in the late Noachian and early Hesperian. These data suggest a tectonic event near the Noachian/Hesperian boundary characterized by enhanced heat loss and extensive fracturing, including formation of the faults that define much of the highland/lowland boundary. It is argued that the major result of this tectonic event was formation of the dichotomy by thinning of the crust above a large convection cell or plume.

Interactions with nanoscale topography: adhesion quantification and signal transduction in cells of osteogenic and multipotent lineage.

PubMed

Biggs, Manus J P; Richards, R Geoff; Gadegaard, Nikolaj; McMurray, Rebecca J; Affrossman, Stanley; Wilkinson, Chris D W; Oreffo, Richard O C; Dalby, Mathew J

2009-10-01

Polymeric medical devices widely used in orthopedic surgery play key roles in fracture fixation and orthopedic implant design. Topographical modification and surface micro-roughness of these devices regulate cellular adhesion, a process fundamental in the initiation of osteoinduction and osteogenesis. Advances in fabrication techniques have evolved the field of surface modification; in particular, nanotechnology has allowed the development of nanoscale substrates for the investigation into cell-nanofeature interactions. In this study human osteoblasts (HOBs) were cultured on ordered nanoscale pits and random nano "craters" and "islands". Adhesion subtypes were quantified by immunofluorescent microscopy and cell-substrate interactions investigated via immuno-scanning electron microscopy. To investigate the effects of these substrates on cellular function 1.7 k microarray analysis was used to establish gene profiles of enriched STRO-1+ progenitor cell populations cultured on these nanotopographies. Nanotopographies affected the formation of adhesions on experimental substrates. Adhesion formation was prominent on planar control substrates and reduced on nanocrater and nanoisland topographies; nanopits, however, were shown to inhibit directly the formation of large adhesions. STRO-1+ progenitor cells cultured on experimental substrates revealed significant changes in genetic expression. This study implicates nanotopographical modification as a significant modulator of osteoblast adhesion and cellular function in mesenchymal populations.

An algorithm-based topographical biomaterials library to instruct cell fate

PubMed Central

Unadkat, Hemant V.; Hulsman, Marc; Cornelissen, Kamiel; Papenburg, Bernke J.; Truckenmüller, Roman K.; Carpenter, Anne E.; Wessling, Matthias; Post, Gerhard F.; Uetz, Marc; Reinders, Marcel J. T.; Stamatialis, Dimitrios; van Blitterswijk, Clemens A.; de Boer, Jan

2011-01-01

It is increasingly recognized that material surface topography is able to evoke specific cellular responses, endowing materials with instructive properties that were formerly reserved for growth factors. This opens the window to improve upon, in a cost-effective manner, biological performance of any surface used in the human body. Unfortunately, the interplay between surface topographies and cell behavior is complex and still incompletely understood. Rational approaches to search for bioactive surfaces will therefore omit previously unperceived interactions. Hence, in the present study, we use mathematical algorithms to design nonbiased, random surface features and produce chips of poly(lactic acid) with 2,176 different topographies. With human mesenchymal stromal cells (hMSCs) grown on the chips and using high-content imaging, we reveal unique, formerly unknown, surface topographies that are able to induce MSC proliferation or osteogenic differentiation. Moreover, we correlate parameters of the mathematical algorithms to cellular responses, which yield novel design criteria for these particular parameters. In conclusion, we demonstrate that randomized libraries of surface topographies can be broadly applied to unravel the interplay between cells and surface topography and to find improved material surfaces. PMID:21949368

Borehole characterization of hydraulic properties and groundwater flow in a crystalline fractured aquifer of a headwater mountain watershed, Laramie Range, Wyoming

NASA Astrophysics Data System (ADS)

Ren, Shuangpo; Gragg, Samuel; Zhang, Ye; Carr, Bradley J.; Yao, Guangqing

2018-06-01

Fractured crystalline aquifers of mountain watersheds may host a significant portion of the world's freshwater supply. To effectively utilize water resources in these environments, it is important to understand the hydraulic properties, groundwater storage, and flow processes in crystalline aquifers and field-derived insights are critically needed. Based on borehole hydraulic characterization and monitoring data, this study inferred hydraulic properties and groundwater flow of a crystalline fractured aquifer in Laramie Range, Wyoming. At three open holes completed in a fractured granite aquifer, both slug tests and FLUTe liner profiling were performed to obtain estimates of horizontal hydraulic conductivity (Kh). Televiewer (i.e., optical and acoustic) and flowmeter logs were then jointly interpreted to identify the number of flowing fractures and fracture zones. Based on these data, hydraulic apertures were obtained for each borehole. Average groundwater velocity was then computed using Kh, aperture, and water level monitoring data. Finally, based on all available data, including cores, borehole logs, LIDAR topography, and a seismic P-wave velocity model, a three dimensional geological model of the site was built. In this fractured aquifer, (1) borehole Kh varies over ∼4 orders of magnitude (10-8-10-5 m/s). Kh is consistently higher near the top of the bedrock that is interpreted as the weathering front. Using a cutoff Kh of 10-10 m/s, the hydraulically significant zone extends to ∼40-53 m depth. (2) FLUTe-estimated hydraulic apertures of fractures vary over 1 order of magnitude, and at each borehole, the average hydraulic aperture by FLUTe is very close to that obtained from slug tests. Thus, slug test can be used to provide a reliable estimate of the average fracture hydraulic aperture. (3) Estimated average effective fracture porosity is 4.0 × 10-4, therefore this fractured aquifer can host significant quantity of water. (4) Natural groundwater velocity is estimated to range from 0.4 to 81.0 m/day, implying rapid pathways of fracture flow. (5) The average ambient water table position follows the boundary between saprolite and fractured bedrock. Groundwater flow at the site appears topography driven.

Enhanced Characterization of Niobium Surface Topography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Xu, Hui Tian, Charles Reece, Michael Kelley

2011-12-01

Surface topography characterization is a continuing issue for the Superconducting Radio Frequency (SRF) particle accelerator community. Efforts are underway to both to improve surface topography, and its characterization and analysis using various techniques. In measurement of topography, Power Spectral Density (PSD) is a promising method to quantify typical surface parameters and develop scale-specific interpretations. PSD can also be used to indicate how chemical processes modifiesy the roughnesstopography at different scales. However, generating an accurate and meaningful topographic PSD of an SRF surface requires careful analysis and optimization. In this report, polycrystalline surfaces with different process histories are sampled with AFMmore » and stylus/white light interferometer profilometryers and analyzed to indicate trace topography evolution at different scales. evolving during etching or polishing. Moreover, Aan optimized PSD analysis protocol will be offered to serve the SRF surface characterization needs is presented.« less

Recent advances in engineering topography mediated antibacterial surfaces

PubMed Central

Hasan, Jafar

2015-01-01

The tendency of bacterial cells to adhere and colonize a material surface leading to biofilm formation is a fundamental challenge underlying many different applications including microbial infections associated with biomedical devices and products. Although, bacterial attachment to surfaces has been extensively studied in the past, the effect of surface topography on bacteria–material interactions has received little attention until more recently. We review the recent progress in surface topography based approaches for engineering antibacterial surfaces. Biomimicry of antibacterial surfaces in nature is a popular strategy. Whereas earlier endeavors in the field aimed at minimizing cell attachment, more recent efforts have focused on developing bactericidal surfaces. However, not all such topography mediated bactericidal surfaces are necessarily cytocompatible thus underscoring the need for continued efforts for research in this area for developing antibacterial and yet cytocompatible surfaces for use in implantable biomedical applications. This mini-review provides a brief overview of the current strategies and challenges in the emerging field of topography mediated antibacterial surfaces. PMID:26372264

Recent advances in engineering topography mediated antibacterial surfaces

NASA Astrophysics Data System (ADS)

Hasan, Jafar; Chatterjee, Kaushik

2015-09-01

The tendency of bacterial cells to adhere and colonize a material surface leading to biofilm formation is a fundamental challenge underlying many different applications including microbial infections associated with biomedical devices and products. Although, bacterial attachment to surfaces has been extensively studied in the past, the effect of surface topography on bacteria-material interactions has received little attention until more recently. We review the recent progress in surface topography based approaches for engineering antibacterial surfaces. Biomimicry of antibacterial surfaces in nature is a popular strategy. Whereas earlier endeavors in the field aimed at minimizing cell attachment, more recent efforts have focused on developing bactericidal surfaces. However, not all such topography mediated bactericidal surfaces are necessarily cytocompatible thus underscoring the need for continued efforts for research in this area for developing antibacterial and yet cytocompatible surfaces for use in implantable biomedical applications. This mini-review provides a brief overview of the current strategies and challenges in the emerging field of topography mediated antibacterial surfaces.

Deconvoluting the effects of surface chemistry and nanoscale topography: Pseudomonas aeruginosa biofilm nucleation on Si-based substrates.

PubMed

Zhang, Jing; Huang, Jinglin; Say, Carmen; Dorit, Robert L; Queeney, K T

2018-06-01

The nucleation of biofilms is known to be affected by both the chemistry and topography of the underlying substrate, particularly when topography includes nanoscale (<100 nm) features. However, determining the role of topography vs. chemistry is complicated by concomitant variation in both as a result of typical surface modification techniques. Analyzing the behavior of biofilm-forming bacteria exposed to surfaces with systematic, independent variation of both topography and surface chemistry should allow differentiation of the two effects. Silicon surfaces with reproducible nanotopography were created by anisotropic etching in deoxygenated water. Surface chemistry was varied independently to create hydrophilic (OH-terminated) and hydrophobic (alkyl-terminated) surfaces. The attachment and proliferation of Psuedomonas aeruginosa to these surfaces was characterized over a period of 12 h using fluorescence and confocal microscopy. The number of attached bacteria as well as the structural characteristics of the nucleating biofilm were influenced by both surface nanotopography and surface chemistry. In general terms, the presence of both nanoscale features and hydrophobic surface chemistry enhance bacterial attachment and colonization. However, the structural details of the resulting biofilms suggest that surface chemistry and topography interact differently on each of the four surface types we studied. Copyright © 2018 Elsevier Inc. All rights reserved.

Hygrothermal influence on delamination behavior of graphite/epoxy laminates

NASA Technical Reports Server (NTRS)

Garg, A.; Ishai, O.

1985-01-01

The hygrothermal effect on the fracture behavior of graphite-epoxy laminates was investigated to develop a methodology for damage tolerance predictions in advanced composite materials. Several T300/934 laminates were tested using a number of specimen configurations to evaluate the effects of temperature and humidity on delamination fracture toughness under mode 1 and mode 2 loading. It is indicated that moisture has a slightly beneficial influence on fracture toughness or critical strain energy release rate during mode 1 delamination, but has a slightly deleterious effect on mode 2 delamination, and mode 1 transverse cracking. The failed specimens are examined by SEM and topographical differences due to fracture modes are identified. It is concluded that the effect of moisture on fracture topography can not be distinguished.

Hygrothermal influence on delamination behavior of graphite/epoxy laminates

NASA Technical Reports Server (NTRS)

Garg, A.; Ishai, O.

1984-01-01

The hygrothermal effect on the fracture behavior of graphite-epoxy laminates was investigated to develop a methodology for damage tolerance predictions in advanced composite materials. Several T300/934 laminates were tested using a number of specimen configurations to evaluate the effects of temperature and humidity on delamination fracture toughness under mode 1 and mode 2 loading. It is indicated that moisture has a slightly beneficial influence on fracture toughness or critical strain energy release rate during mode 1 delamination, but has a slightly deleterious effect on mode 2 delamination and mode 1 transverse cracking. The failed specimens are examined by SEM and topographical differences due to fracture modes are identified. It is concluded that the effect of moisture on fracture topography can not be distinguished.

Analysis of high-throughput screening reveals the effect of surface topographies on cellular morphology.

PubMed

Hulsman, Marc; Hulshof, Frits; Unadkat, Hemant; Papenburg, Bernke J; Stamatialis, Dimitrios F; Truckenmüller, Roman; van Blitterswijk, Clemens; de Boer, Jan; Reinders, Marcel J T

2015-03-01

Surface topographies of materials considerably impact cellular behavior as they have been shown to affect cell growth, provide cell guidance, and even induce cell differentiation. Consequently, for successful application in tissue engineering, the contact interface of biomaterials needs to be optimized to induce the required cell behavior. However, a rational design of biomaterial surfaces is severely hampered because knowledge is lacking on the underlying biological mechanisms. Therefore, we previously developed a high-throughput screening device (TopoChip) that measures cell responses to large libraries of parameterized topographical material surfaces. Here, we introduce a computational analysis of high-throughput materiome data to capture the relationship between the surface topographies of materials and cellular morphology. We apply robust statistical techniques to find surface topographies that best promote a certain specified cellular response. By augmenting surface screening with data-driven modeling, we determine which properties of the surface topographies influence the morphological properties of the cells. With this information, we build models that predict the cellular response to surface topographies that have not yet been measured. We analyze cellular morphology on 2176 surfaces, and find that the surface topography significantly affects various cellular properties, including the roundness and size of the nucleus, as well as the perimeter and orientation of the cells. Our learned models capture and accurately predict these relationships and reveal a spectrum of topographies that induce various levels of cellular morphologies. Taken together, this novel approach of high-throughput screening of materials and subsequent analysis opens up possibilities for a rational design of biomaterial surfaces. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Significance of Thermal Fluvial Incision and Bedrock Transfer due to Ice Advection on Greenland Ice Sheet Topography

NASA Astrophysics Data System (ADS)

Crozier, J. A.; Karlstrom, L.; Yang, K.

2017-12-01

Ice sheet surface topography reflects a complicated combination of processes that act directly upon the surface and that are products of ice advection. Using recently-available high resolution ice velocity, imagery, ice surface elevation, and bedrock elevation data sets, we seek to determine the domain of significance of two important processes - thermal fluvial incision and transfer of bedrock topography through the ice sheet - on controlling surface topography in the ablation zone. Evaluating such controls is important for understanding how melting of the GIS surface during the melt season may be directly imprinted in topography through supraglacial drainage networks, and indirectly imprinted through its contribution to basal sliding that affects bedrock transfer. We use methods developed by (Karlstrom and Yang, 2016) to identify supraglacial stream networks on the GIS, and use high resolution surface digital elevation models as well as gridded ice velocity and melt rate models to quantify surface processes. We implement a numerically efficient Fourier domain bedrock transfer function (Gudmundsson, 2003) to predict surface topography due to ice advection over bedrock topography obtained from radar. Despite a number of simplifying assumptions, the bedrock transfer function predicts the observed ice sheet surface in most regions of the GIS with ˜90% accuracy, regardless of the presence or absence of supraglacial drainage networks. This supports the hypothesis that bedrock is the most significant driver of ice surface topography on wavelengths similar to ice thickness. Ice surface topographic asymmetry on the GIS is common, with slopes in the direction of ice flow steeper than those faced opposite to ice flow, consistent with bedrock transfer theory. At smaller wavelengths, topography consistent with fluvial erosion by surface hydrologic features is evident. We quantify the effect of ice advection versus fluvial thermal erosion on supraglacial longitudinal stream profiles, as a function of location on the GIS (hence ice thickness and background melt rate) using spectral techniques to quantify longitudinal stream profiles. This work should provide a predictive guide for which processes are responsible for ice sheet topography scales from several m (DEM resolution) up to several ice thicknesses.

Simulation of ground-water flow to assess geohydrologic factors and their effect on source-water areas for bedrock wells in Connecticut

USGS Publications Warehouse

Starn, J. Jeffrey; Stone, Janet Radway

2005-01-01

Generic ground-water-flow simulation models show that geohydrologic factors?fracture types, fracture geometry, and surficial materials?affect the size, shape, and location of source-water areas for bedrock wells. In this study, conducted by the U.S. Geological Survey in cooperation with the Connecticut Department of Public Health, ground-water flow was simulated to bedrock wells in three settings?on hilltops and hillsides with no surficial aquifer, in a narrow valley with a surficial aquifer, and in a broad valley with a surficial aquifer?to show how different combinations of geohydrologic factors in different topographic settings affect the dimensions and locations of source-water areas in Connecticut. Three principal types of fractures are present in bedrock in Connecticut?(1) Layer-parallel fractures, which developed as partings along bedding in sedimentary rock and compositional layering or foliation in metamorphic rock (dips of these fractures can be gentle or steep); (2) unroofing joints, which developed as strain-release fractures parallel to the land surface as overlying rock was removed by erosion through geologic time; and (3) cross fractures and joints, which developed as a result of tectonically generated stresses that produced typically near-vertical or steeply dipping fractures. Fracture geometry is defined primarily by the presence or absence of layering in the rock unit, and, if layered, by the angle of dip in the layering. Where layered rocks dip steeply, layer-parallel fracturing generally is dominant; unroofing joints also are typically well developed. Where layered rocks dip gently, layer-parallel fracturing also is dominant, and connections among these fractures are provided only by the cross fractures. In gently dipping rocks, unroofing joints generally do not form as a separate fracture set; instead, strain release from unroofing has occurred along gently dipping layer-parallel fractures, enhancing their aperture. In nonlayered and variably layered rocks, layer-parallel fracturing is absent or poorly developed; fracturing is dominated by well-developed subhorizontal unroofing joints and steeply dipping, tectonically generated fractures and (or) cooling joints. Cross fractures (or cooling joints) in nonlayered and variably layered rocks have more random orientations than in layered rocks. Overall, nonlayered or variably layered rocks do not have a strongly developed fracture direction. Generic ground-water-flow simulation models showed that fracture geometry and other geohydrologic factors affect the dimensions and locations of source-water areas for bedrock wells. In general, source-water areas to wells reflect the direction of ground-water flow, which mimics the land-surface topography. Source-water areas to wells in a hilltop setting were not affected greatly by simulated fracture zones, except for an extensive vertical fracture zone. Source-water areas to wells in a hillside setting were not affected greatly by simulated fracture zones, except for the combination of a subhorizontal fracture zone and low bedrock vertical hydraulic conductivity, as might be the case where an extensive subhorizontal fracture zone is not connected or is poorly connected to the surface through vertical fractures. Source-water areas to wells in a narrow valley setting reflect complex ground-water-flow paths. The typical flow path originates in the uplands and passes through either till or bedrock into the surficial aquifer, although only a small area of the surficial aquifer actually contributes water to the well. Source-water areas in uplands can include substantial areas on both sides of a river. Source-water areas for wells in this setting are affected mainly by the rate of ground-water recharge and by the degree of anisotropy. Source-water areas to wells in a broad valley setting (bedrock with a low angle of dip) are affected greatly by fracture properties. The effect of a given fracture is to channel the

Deformation behavior of micro-indentation defects under uniaxial and biaxial loads

NASA Astrophysics Data System (ADS)

Ma, Zhichao; Zhao, Hongwei; Lu, Shuai; Li, Hailian; Liu, Changyi; Liu, Xianhua

2015-09-01

The microdefects of structure frequently act as the source to generate initial cracks and lead to the fracture failure. Study on the deformation behaviors of embedded defects would be conducive to better understand the failure mechanisms of structural materials. Micro-indentation technique was applied to prepare the initial indentations as embedded surface defects at the gauge length section and central section of a cross-shaped AZ31B magnesium alloy specimen. A novel in situ biaxial tensile device was developed to apply the synchronous biaxial loads. Via the observation by an optical microscope with three-dimensional imaging and measurement functions, the changing laws of the indentation topographies under uniaxial and biaxial tensile loads were discussed. Compared with the gauge length section, the increasing trend of the indentation length of the central section was relatively flat, and the decreasing trend of the indentation depth was more significant. The changes of indentation topographies were explained by the Poisson effect, and the significant plastic tensile stress has led to the releasing of the residual stress around the indentation location and also promoted the planarization of the pileup.

Deformation behavior of micro-indentation defects under uniaxial and biaxial loads.

PubMed

Ma, Zhichao; Zhao, Hongwei; Lu, Shuai; Li, Hailian; Liu, Changyi; Liu, Xianhua

2015-09-01

The microdefects of structure frequently act as the source to generate initial cracks and lead to the fracture failure. Study on the deformation behaviors of embedded defects would be conducive to better understand the failure mechanisms of structural materials. Micro-indentation technique was applied to prepare the initial indentations as embedded surface defects at the gauge length section and central section of a cross-shaped AZ31B magnesium alloy specimen. A novel in situ biaxial tensile device was developed to apply the synchronous biaxial loads. Via the observation by an optical microscope with three-dimensional imaging and measurement functions, the changing laws of the indentation topographies under uniaxial and biaxial tensile loads were discussed. Compared with the gauge length section, the increasing trend of the indentation length of the central section was relatively flat, and the decreasing trend of the indentation depth was more significant. The changes of indentation topographies were explained by the Poisson effect, and the significant plastic tensile stress has led to the releasing of the residual stress around the indentation location and also promoted the planarization of the pileup.

Constraints on mechanisms for the growth of gully alcoves in Gasa crater, Mars, from two-dimensional stability assessments of rock slopes

USGS Publications Warehouse

Okubo, C.H.; Tornabene, L.L.; Lanza, N.L.

2011-01-01

The value of slope stability analyses for gaining insight into the geologic conditions that would facilitate the growth of gully alcoves on Mars is demonstrated in Gasa crater. Two-dimensional limit equilibrium methods are used in conjunction with high-resolution topography derived from stereo High Resolution Imaging Science Experiment (HiRISE) imagery. These analyses reveal three conditions that may produce observed alcove morphologies through slope failure: (1) a ca >10m thick surface layer that is either saturated with H2O ground ice or contains no groundwater/ice at all, above a zone of melting H2O ice or groundwater and under dynamic loading (i.e., seismicity), (2) a 1-10m thick surface layer that is saturated with either melting H2O ice or groundwater and under dynamic loading, or (3) a >100m thick surface layer that is saturated with either melting H2O ice or groundwater and under static loading. This finding of three plausible scenarios for slope failure demonstrates how the triggering mechanisms and characteristics of future alcove growth would be affected by prevailing environmental conditions. HiRISE images also reveal normal faults and other fractures tangential to the crowns of some gully alcoves that are interpreted to be the result of slope instability, which may facilitate future slope movement. Stability analyses show that the most failure-prone slopes in this area are found in alcoves that are adjacent to crown fractures. Accordingly, crown fractures appear to be a useful indicator of those alcoves that should be monitored for future landslide activity. ?? 2010.

New Electrical Resistivity Tomography approach for karst cave characterization: Castello di Lepre karst cave (Marsico Nuovo, Southern Italy).

NASA Astrophysics Data System (ADS)

Guerriero, Merilisa; Capozzoli, Luigi; De Martino, Gregory; Perciante, Felice; Gueguen, Erwan; Rizzo, Enzo

2017-04-01

Geophysical methods are commonly applied to characterize karst cave. Several geophysical method are used such as electrical resistivity tomography (ERT), gravimetric prospecting (G), ground penetrating radar (GPR) and seismic methods (S), in order to provide information on cave geometry and subsurface geological structure. In detail, in some complex karst systems, each geophysical method can only give partial information if used in normal way due to a low resolution for deep target. In order to reduce uncertainty and avoid misinterpretations based on a normal use of the electrical resistivity tomography method, a new ERT approach has been applied in karst cave Castello di Lepre (Marsico Nuovo, Basilicata region, Italy) located in the Mezo-Cenozoic carbonate substratum of the Monti della Maddalena ridge (Southern Appenines). In detail, a cross-ERT acquisition system was applied in order to improve the resolution on the electrical resistivity distribution on the surrounding geological structure of a karst cave. The cross-ERT system provides a more uniform model resolution vertically, increasing the resolution of the surface resistivity imaging. The usual cross-ERT is made by electrode setting in two or more borehole in order to acquire the resistivity data distribution. In this work the cross-ERT was made between the electrodes located on surface and along a karst cave, in order to obtain an high resolution of the electrical resistivity distributed between the cave and the surface topography. Finally, the acquired cross-ERT is potentially well-suited for imaging fracture zones since electrical current flow in fractured rock is primarily electrolytic via the secondary porosity associated with the fractures.

Is there more to the clinical outcome in posttraumatic reconstruction of the inferior and medial orbital walls than accuracy of implant placement and implant surface contouring? A prospective multicenter study to identify predictors of clinical outcome.

PubMed

Zimmerer, Rüdiger M; Gellrich, Nils-Claudius; von Bülow, Sophie; Strong, Edward Bradley; Ellis, Edward; Wagner, Maximilian E H; Sanchez Aniceto, Gregorio; Schramm, Alexander; Grant, Michael P; Thiam Chye, Lim; Rivero Calle, Alvaro; Wilde, Frank; Perez, Daniel; Bittermann, Gido; Mahoney, Nicholas R; Redondo Alamillos, Marta; Bašić, Joanna; Metzger, Marc; Rasse, Michael; Dittman, Jan; Rometsch, Elke; Espinoza, Kathrin; Hesse, Ronny; Cornelius, Carl-Peter

2018-04-01

Reconstruction of orbital wall fractures is demanding and has improved dramatically with the implementation of new technologies. True-to-original accuracy of reconstruction has been deemed essential for good clinical outcome, and reasons for unfavorable clinical outcome have been researched extensively. However, no detailed analysis on the influence of plate position and surface contour on clinical outcome has yet been published. Data from a previous study were used for an ad-hoc analysis to identify predictors for unfavorable outcome, defined as diplopia or differences in globe height and/or globe projection of >2 mm. Presumed predictors were implant surface contour, aberrant implant dimension or position, accuracy of reconstructed orbital volume, and anatomical fracture topography according to the current AO classification. Neither in univariable nor in multivariable regression models were unfavorable clinical outcomes associated with any of the presumed radiological predictors, and no association of the type of implant, i.e., standard preformed, CAD-based individualized and non-CAD-based individualized with its surface contour could be shown. These data suggest that the influence of accurate mechanical reconstruction on clinical outcomes may be less predictable than previously believed, while the role of soft-tissue-related factors may have been underestimated. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Analysis of the fractures of metallic materials using optical coherence tomography

NASA Astrophysics Data System (ADS)

Hutiu, Gh.; Duma, V.-F.; Demian, D.; Bradu, A.; Podoleanu, A. Gh.

2017-06-01

Forensic in situ investigations, for example for aviation, maritime, road, or rail accidents would benefit from a method that may allow to distinguish ductile from brittle fractures of metals - as material defects are one of the potential causes of such accidents. Currently, the gold standard in material studies is represented by scanning electron microscopy (SEM). However, SEM are large, lab-based systems, therefore in situ measurements are excluded. In addition, they are expensive and time-consuming. We have approached this problem and propose the use of Optical Coherence Tomography (OCT) in such investigations in order to overcome these disadvantages of SEM. In this respect, we demonstrate the capability to perform such fracture analysis by obtaining the topography of metallic surfaces using OCT. Different materials have been analyzed; in this presentation a sample of low soft carbon steel with the chemical composition of C 0.2%, Mn 1.15%, S 0.04%, P 0.05 % and Fe for the rest has been considered. An in-house developed Swept Source (SS) OCT system has been used, and height profiles have been generated for the sample surface. This profile allowed for concluding that the carbon steel sample was subjected to a ductile fracture. A validation of the OCT images obtained with a 10 microns resolution has been made with SEM images obtained with a 4 nm resolution. Although the OCT resolution is much lower than the one of SEM, we thus demonstrate that it is sufficient in order to obtain clear images of the grains of the metallic materials and thus to distinguish between ductile and brittle fractures. This study analysis opens avenues for a range of applications, including: (i) to determine the causes that have generated pipe ruptures, or structural failures of metallic bridges and buildings, as well as damages of machinery parts; (ii) to optimize the design of various machinery; (iii) to obtain data regarding the structure of metallic alloys); (iv) to improve the manufacturing technologies of metallic parts.

Fracture toughness and fracture behavior of CLAM steel in the temperature range of 450 °C-550 °C

NASA Astrophysics Data System (ADS)

Zhao, Yanyun; Liang, Mengtian; Zhang, Zhenyu; Jiang, Man; Liu, Shaojun

2018-04-01

In order to analyze the fracture toughness and fracture behavior (J-R curves) of China Low Activation Martensitic (CLAM) steel under the design service temperature of Test Blanket Module of the International Thermonuclear Experimental Reactor, the quasi-static fracture experiment of CLAM steel was carried out under the temperature range of 450 °C-550 °C. The results indicated that the fracture behavior of CLAM steel was greatly influenced by test temperature. The fracture toughness increased slightly as the temperature increased from 450 °C to 500 °C. In the meanwhile, the fracture toughness at 550 °C could not be obtained due to the plastic deformation near the crack tip zone. The microstructure analysis based on the fracture topography and the interaction between dislocations and lath boundaries showed two different sub-crack propagation modes: growth along 45° of the main crack direction at 450 °C and growth perpendicular to the main crack at 500 °C.

Tuning cell adhesion on polymeric and nanocomposite surfaces: Role of topography versus superhydrophobicity.

PubMed

Zangi, Sepideh; Hejazi, Iman; Seyfi, Javad; Hejazi, Ehsan; Khonakdar, Hossein Ali; Davachi, Seyed Mohammad

2016-06-01

Development of surface modification procedures which allow tuning the cell adhesion on the surface of biomaterials and devices is of great importance. In this study, the effects of different topographies and wettabilities on cell adhesion behavior of polymeric surfaces are investigated. To this end, an improved phase separation method was proposed to impart various wettabilities (hydrophobic and superhydrophobic) on polypropylene surfaces. Surface morphologies and compositions were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Cell culture was conducted to evaluate the adhesion of 4T1 mouse mammary tumor cells. It was found that processing conditions such as drying temperature is highly influential in cell adhesion behavior due to the formation of an utterly different surface topography. It was concluded that surface topography plays a more significant role in cell adhesion behavior rather than superhydrophobicity since the nano-scale topography highly inhibited the cell adhesion as compared to the micro-scale topography. Such cell repellent behavior could be very useful in many biomedical devices such as those in drug delivery and blood contacting applications as well as biosensors. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of Topography-based Subgrid Structures on Land Surface Modeling

NASA Astrophysics Data System (ADS)

Tesfa, T. K.; Ruby, L.; Brunke, M.; Thornton, P. E.; Zeng, X.; Ghan, S. J.

2017-12-01

Topography has major control on land surface processes through its influence on atmospheric forcing, soil and vegetation properties, network topology and drainage area. Consequently, accurate climate and land surface simulations in mountainous regions cannot be achieved without considering the effects of topographic spatial heterogeneity. To test a computationally less expensive hyper-resolution land surface modeling approach, we developed topography-based landunits within a hierarchical subgrid spatial structure to improve representation of land surface processes in the ACME Land Model (ALM) with minimal increase in computational demand, while improving the ability to capture the spatial heterogeneity of atmospheric forcing and land cover influenced by topography. This study focuses on evaluation of the impacts of the new spatial structures on modeling land surface processes. As a first step, we compare ALM simulations with and without subgrid topography and driven by grid cell mean atmospheric forcing to isolate the impacts of the subgrid topography on the simulated land surface states and fluxes. Recognizing that subgrid topography also has important effects on atmospheric processes that control temperature, radiation, and precipitation, methods are being developed to downscale atmospheric forcings. Hence in the second step, the impacts of the subgrid topographic structure on land surface modeling will be evaluated by including spatial downscaling of the atmospheric forcings. Preliminary results on the atmospheric downscaling and the effects of the new spatial structures on the ALM simulations will be presented.

Multi-scale geophysical study to model the distribution and development of fractures in relation to the knickpoint in the Luquillo Critical Zone Observatory (Puerto Rico)

NASA Astrophysics Data System (ADS)

Comas, X.; Wright, W. J.; Hynek, S. A.; Ntarlagiannis, D.; Terry, N.; Job, M. J.; Fletcher, R. C.; Brantley, S.

2017-12-01

Previous studies in the Rio Icacos watershed in the Luquillo Mountains (Puerto Rico) have shown that regolith materials are rapidly developed from the alteration of quartz diorite bedrock, and create a blanket on top of the bedrock with a thickness that decreases with proximity to the knickpoint. The watershed is also characterized by a system of heterogeneous fractures that likely drive bedrock weathering and the formation of corestones and associated spheroidal fracturing and rindlets. Previous efforts to characterize the spatial distribution of fractures were based on aerial images that did not account for the architecture of the critical zone below the subsurface. In this study we use an array of near-surface geophysical methods at multiple scales to better understand how the spatial distribution and density of fractures varies with topography and proximity to the knickpoint. Large km-scale surveys using ground penetrating radar (GPR), terrain conductivity, and capacitively coupled resistivity, were combined with smaller scale surveys (10-100 m) using electrical resistivity imaging (ERI), and shallow seismics, and were directly constrained with boreholes from previous studies. Geophysical results were compared to theoretical models of compressive stress as due to gravity and regional compression, and showed consistency at describing increased dilation of fractures with proximity to the knickpoint. This study shows the potential of multidisciplinary approaches to model critical zone processes at multiple scales of measurement and high spatial resolution. The approach can be particularly efficient at large km-scales when applying geophysical methods that allow for rapid data acquisition (i.e. walking pace) at high spatial resolution (i.e. cm scales).

Dynamic Topography at Earth's Surface: Fact or Fiction? (Invited)

NASA Astrophysics Data System (ADS)

Lithgow-Bertelloni, C. R.; Silver, P. G.

2009-12-01

Contributions to Earth’s surface topography range from short-wavelength uncompensated features due to tectonic activity, to variations in crustal structure and long-wavelength deflections of the lithosphere caused by mantle dynamics. The latter we call dynamic topography. Dynamic topography elevates or depresses the surface even if the density anomaly giving rise to flow is deep in the mantle. Dynamic topography is also a major contributor to Earth’s gravitational potential and to surface deformation. However, direct observations of dynamic topography are elusive, because signals are obscured by the isostatic contribution due to crustal and lithospheric structure. The only seemingly unequivocal signals of dynamically supported topography have been found over mantle upwellings on both continents (Africa [Lithgow-Bertelloni and Silver, 1998] and Arabia [Daradich et al., 2004]) and oceanic basins (North-Atlantic [Conrad et al., 2004]). Recent work on Africa’s geomorphic history [Moore et al., 2009] and North Atlantic gravity and topography have called even these results into questions. In downwelling regions (near slabs) no clear signals have been found. I will explore why this dichotomy may exist and relate it to the need for dynamic topography in mantle flow models, with an eye towards the effects of phase transitions, lateral variations in viscosity and layered convection. I will also present recent results on dynamic topography over flat slab segments that overturn the conventional wisdom and explain basin topography in the Andean foreland. Along with the new models I will discuss a recent global lithospheric structure model with which to compute the residual topography, i.e. the “observed” dynamic topography.

ARC-1979-A79-7093

NASA Image and Video Library

1979-07-09

Range : 225,000 kilometers (140,625 miles) This image of the Jovian moon Europa was taken by Voyager 2 along the evening terminator, which best shows the surface topography of complex narrow ridges, seen as curved bright streaks, 5 to 10 kilometers wide, and typically 100 kilometers in length. The area shown is about 600 by 800 kilometers, and the smallest features visible are about 4 kilometers in size. Also visable are dark bands, more diffused in character, 20 to 40 kilometers wide and hundreds to thousands of kilometers in length. A few features are suggestive of impact craters but are rare, indication that the surface thought to be dominantly ice is still active, perhaps warmed by tidal heating like Io. The larger icy satellites, Callisto and Ganymede, are evidently colder with much more rigid crusts and ancient impact craters. The complex intersection of dark markings and bright ridges suggest that the surface has been fractured and material from beneath has welled up to fill the cracks.

Modeling a Shallow Rock Tunnel Using Terrestrial Laser Scanning and Discrete Fracture Networks

NASA Astrophysics Data System (ADS)

Cacciari, Pedro Pazzoto; Futai, Marcos Massao

2017-05-01

Discontinuity mapping and analysis are extremely important for modeling shallow tunnels constructed in fractured rock masses. However, the limited exposure and variability of rock face orientation in tunnels must be taken into account. In this paper, an automatic method is proposed to generate discrete fracture networks (DFNs) using terrestrial laser scanner (TLS) geological mapping and to continuously calculate the volumetric intensities ( P 32) along a tunnel. The number of fractures intersecting rectangular sampling planes with different orientations, fitted in tunnel sections of finite lengths, is used as the program termination criteria to create multiple DFNs and to calculate the mean P 32. All traces and orientations from three discontinuity sets of the Monte Seco tunnel (Vitória Minas Railway) were mapped and the present method applied to obtain the continuous variation in P 32 along the tunnel. A practical approach to creating single and continuous DFNs (for each discontinuity set), considering the P 32 variations, is also presented, and the results are validated by comparing the trace intensities ( P 21) from the TLS mapping and DFNs generated. Three examples of 3DEC block models generated from different sections of the tunnel are shown, including the ground surface and the bedrock topographies. The results indicate that the proposed method is a practical and powerful tool for modeling fractured rock masses of uncovered tunnels. It is also promising for application during tunnel construction when TLS mapping is a daily task (for as-built tunnel controls), and the complete geological mapping (traces and orientations) is available.

Influence of substrate preparation on the shaping of the topography of the surface of nanoceramic oxide layers

NASA Astrophysics Data System (ADS)

Bara, Marek; Kubica, Marek

2014-02-01

The paper discusses the shaping mechanism and changes occurring in the structure and topography of the surface of nanoceramic oxide layers during their formation. The paper presents the influence of substrate preparation on the surface topography of oxide layers. The layers were produced via hard anodizing on the EN AW-5251 aluminum alloy. The layers obtained were subjected to microscope examinations, image and chemical composition analyses, and stereometric examinations. Heredity of substrate properties in the topography of the surface of nanoceramic oxide layers formed as a result of electrochemical oxidation has been shown.

Ocean Surface Topography Mission/Jason 2 Artist Concept

NASA Image and Video Library

2008-09-23

An artist concept of the Ocean Surface Topography Mission/Jason 2 Earth satellite. The Ocean Surface Topography Mission/Jason 2 is an Earth satellite designed to make observations of ocean topography for investigations into sea-level rise and the relationship between ocean circulation and climate change. The satellite also provides data on the forces behind such large-scale climate phenomena as El Niño and La Niña. The mission is a follow-on to the French-American Jason 1 mission, which began collecting data on sea-surface levels in 1992. http://photojournal.jpl.nasa.gov/catalog/PIA18158

The differential regulation of osteoblast and osteoclast activity by surface topography of hydroxyapatite coatings.

PubMed

Costa, Daniel O; Prowse, Paul D H; Chrones, Tom; Sims, Stephen M; Hamilton, Douglas W; Rizkalla, Amin S; Dixon, S Jeffrey

2013-10-01

The behavior of bone cells is influenced by the surface chemistry and topography of implants and scaffolds. Our purpose was to investigate how the topography of biomimetic hydroxyapatite (HA) coatings influences the attachment and differentiation of osteoblasts, and the resorptive activity of osteoclasts. Using strategies reported previously, we directly controlled the surface topography of HA coatings on polycaprolactone discs. Osteoblasts and osteoclasts were incubated on HA coatings having distinct isotropic topographies with submicrometer and micro-scale features. Osteoblast attachment and differentiation were greater on more complex, micro-rough HA surfaces (Ra ~2 μm) than on smoother topographies (Ra ~1 μm). In contrast, activity of the osteoclast marker tartrate-resistant acid phosphatase was greater on smoother than on micro-rough surfaces. Furthermore, scanning electron microscopy revealed the presence of resorption lacunae exclusively on smoother HA coatings. Inhibition of resorption on micro-rough surfaces was associated with disruption of filamentous actin sealing zones. In conclusion, HA coatings can be prepared with distinct topographies, which differentially regulate responses of osteoblasts, as well as osteoclastic activity and hence susceptibility to resorption. Thus, it may be possible to design HA coatings that induce optimal rates of bone formation and degradation specifically tailored for different applications in orthopedics and dentistry. Copyright © 2013 Elsevier Ltd. All rights reserved.

Surface topography of hydroxyapatite promotes osteogenic differentiation of human bone marrow mesenchymal stem cells.

PubMed

Yang, Wanlei; Han, Weiqi; He, Wei; Li, Jianlei; Wang, Jirong; Feng, Haotian; Qian, Yu

2016-03-01

Effective and safe induction of osteogenic differentiation is one of the key elements of bone tissue engineering. Surface topography of scaffold materials was recently found to promote osteogenic differentiation. Utilization of this topography may be a safer approach than traditional induction by growth factors or chemicals. The aim of this study is to investigate the enhancement of osteogenic differentiation by surface topography and its mechanism of action. Hydroxyapatite (HA) discs with average roughness (Ra) of surface topography ranging from 0.2 to 1.65 μm and mean distance between peaks (RSm) ranging from 89.7 to 18.6 μm were prepared, and human bone-marrow mesenchymal stem cells (hBMSCs) were cultured on these discs. Optimal osteogenic differentiation was observed on discs with surface topography characterized by Ra ranging from 0.77 to 1.09 μm and RSm ranging from 53.9 to 39.3 μm. On this surface configuration of HA, hBMSCs showed oriented attachment, F-actin arrangement, and a peak in the expression of Yes-associated protein (YAP) and PDZ binding motif (TAZ) (YAP/TAZ). These results indicated that the surface topography of HA promoted osteogenic differentiation of hBMSCs, possibly by increasing cell attachment and promoting the YAP/TAZ signaling pathway. Copyright © 2015 Elsevier B.V. All rights reserved.

Activation of Osteoblastic Function on Titanium Surface with Titanium-Doped Hydroxyapatite Nanoparticle Coating: An In Vitro Study.

PubMed

Nakazawa, Masahiro; Yamada, Masahiro; Wakamura, Masato; Egusa, Hiroshi; Sakurai, Kaoru

Titanium-doped hydroxyapatite (TiHA) nanoparticles contain titanium atoms in the hydroxyapatite lattice, which can physicochemically functionalize the titanium surface without modification of the surface topography. This study aimed to evaluate the physicochemical properties of machined or microroughened titanium surfaces coated with TiHA nanoparticles and the functions of osteoblasts cultured on them. Titanium disks with commercially available surface topography, such as machined or sandblasted, large-grit, and acid-etched (SLA) surfaces, were coated with TiHA. The disks with original or TiHA-coated surfaces were evaluated in topography, wettability, and chemical composition. Osteoblastic cells from rat femurs were cultured on the disks and evaluated in proliferation and differentiation. TiHA coating changed from hydrophobicity to hydrophilicity on both machined and SLA surfaces. Calcium and phosphate atoms were detected all over the surface with TiHA coating regardless of the surface topography. However, the considerable change in the inherent surface topographies was not observed on both types of surfaces after TiHA coating. Osteoblastic proliferative activity at day 4 was increased by TiHA coating on both types of surfaces. TiHA coating did not enhance expressions of bone matrix-related genes such as osteocalcin, osteopontin, bone sialoprotein, alkaline phosphatase, and collagen I. However, depositions of collagen, osteocalcin, and calcium in the culture at days 7 and 20 were increased on both types of surface topographies with TiHA coating. TiHA coating enhanced extracellular matrix formation on smooth and microroughened titanium surfaces by increasing osteoblastic proliferative activity without the deterioration of differentiation through hydrophilic and chemical functionalization.

Exact three-dimensional spectral solution to surface-groundwater interactions with arbitrary surface topography

USGS Publications Warehouse

Worman, A.; Packman, A.I.; Marklund, L.; Harvey, J.W.; Stone, S.H.

2006-01-01

It has been long known that land surface topography governs both groundwater flow patterns at the regional-to-continental scale and on smaller scales such as in the hyporheic zone of streams. Here we show that the surface topography can be separated in a Fourier-series spectrum that provides an exact solution of the underlying three-dimensional groundwater flows. The new spectral solution offers a practical tool for fast calculation of subsurface flows in different hydrological applications and provides a theoretical platform for advancing conceptual understanding of the effect of landscape topography on subsurface flows. We also show how the spectrum of surface topography influences the residence time distribution for subsurface flows. The study indicates that the subsurface head variation decays exponentially with depth faster than it would with equivalent two-dimensional features, resulting in a shallower flow interaction. Copyright 2006 by the American Geophysical Union.

Nanotubular topography enhances the bioactivity of titanium implants.

PubMed

Huang, Jingyan; Zhang, Xinchun; Yan, Wangxiang; Chen, Zhipei; Shuai, Xintao; Wang, Anxun; Wang, Yan

2017-08-01

Surface modification on titanium implants plays an important role in promoting mesenchymal stem cell (MSC) response to enhance osseointegration persistently. In this study, nano-scale TiO 2 nanotube topography (TNT), micro-scale sand blasted-acid etched topography (SLA), and hybrid sand blasted-acid etched/nanotube topography (SLA/TNT) were fabricated on the surfaces of titanium implants. Although the initial cell adherence at 60 min among TNT, SLA and TNT/SLA was not different, SLA and SLA/TNT presented to be rougher and suppressed the proliferation of MSC. TNT showed hydrophilic surface and balanced promotion of cellular functions. After being implanted in rabbit femur models, TNT displayed the best osteogenesis inducing ability as well as strong bonding strength to the substrate. These results indicate that nano-scale TNT provides favorable surface topography for improving the clinical performance of endosseous implants compared with micro and hybrid micro/nano surfaces, suggesting a promising and reliable surface modification strategy of titanium implants for clinical application. Copyright © 2017 Elsevier Inc. All rights reserved.

Geology and preliminary hydrogeologic characterization of the cell-house site, Berlin, New Hampshire, 2003-04

USGS Publications Warehouse

Degnan, James R.; Clark, Stewart F.; Harte, Philip T.; Mack, Thomas J.

2005-01-01

At the cell-house site, thin, generally less than 20-foot thick overburden, consisting of till and demolition materials, overlies fractured crystalline bedrock. Bedrock at the site consists of gneiss with thin discontinuous lenses of chlorite schist and discontinuous tabular pegmatite. Two distinct fracture domains, with principal trends to the west and northwest, and to the north, overlap near the site. The cell-house site shows principal trends common to both domains. Gneiss is the most abundant rock at the site. Steeply dipping fractures within the gneiss terminate on subhorizontal contacts with pegmatite and on moderately dipping contacts with chlorite schist. Steeply northwest-dipping en Echelon fracture zones, parallel joint zones, and silicified brittle faults show consistent strikes to the northeast. Gently east-dipping to subhorizontal fractures, sub-parallel to gneissosity, strike northeast. The impermeable cap, barrier wall, and bedrock surface topography affect ground-water flow in the overburden. There is relatively little ground-water flow in the overburden in the capped area and a poor hydraulic connection between the overburden and the underlying bedrock over most of the site. The overburden beneath the cap may receive inflow through or beneath the barrier wall, or by flow through vertical fractures in the underlying bedrock beneath the barrier wall. The bedrock aquifer near the river is well connected to the river and head difference in the bedrock across the site are large (greater than 13 ft). Horizontal hydraulic conductivities of 0.2 to 20 ft/d were estimated for the bedrock. Individual fractures or fracture zones likely have hydraulic conductivities greater than the bulk rock. Subhorizontal fractures occur at pegmatite contacts or along chlorite schist lenses and may serve as ground-water conduits to the steeply dipping fractures in gneiss. The effective hydraulic conductivity across the site is likely to be in the low range of the estimated values (0.2 ft/d). Ground water discharges to the river from the bedrock aquifer and is greatest during periods of large river stage fluctuations.

Surface topography analysis and performance on post-CMP images (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lee, Jusang; Bello, Abner F.; Kakita, Shinichiro; Pieniazek, Nicholas; Johnson, Timothy A.

2017-03-01

Surface topography on post-CMP processing can be measured with white light interference microscopy to determine the planarity. Results are used to avoid under or over polishing and to decrease dishing. The numerical output of the surface topography is the RMS (root-mean-square) of the height. Beyond RMS, the topography image is visually examined and not further quantified. Subjective comparisons of the height maps are used to determine optimum CMP process conditions. While visual comparison of height maps can determine excursions, it's only through manual inspection of the images. In this work we describe methods of quantifying post-CMP surface topography characteristics that are used in other technical fields such as geography and facial-recognition. The topography image is divided into small surface patches of 7x7 pixels. Each surface patch is fitted to an analytic surface equation, in this case a third order polynomial, from which the gradient, directional derivatives, and other characteristics are calculated. Based on the characteristics, the surface patch is labeled as peak, ridge, flat, saddle, ravine, pit or hillside. The number of each label and thus the associated histogram is then used as a quantified characteristic of the surface topography, and could be used as a parameter for SPC (statistical process control) charting. In addition, the gradient for each surface patch is calculated, so the average, maximum, and other characteristics of the gradient distribution can be used for SPC. Repeatability measurements indicate high confidence where individual labels can be lower than 2% relative standard deviation. When the histogram is considered, an associated chi-squared value can be defined from which to compare other measurements. The chi-squared value of the histogram is a very sensitive and quantifiable parameter to determine the within wafer and wafer-to-wafer topography non-uniformity. As for the gradient histogram distribution, the chi-squared could again be calculated and used as yet another quantifiable parameter for SPC. In this work we measured the post Cu CMP of a die designed for 14nm technology. A region of interest (ROI) known to be indicative of the CMP processing is chosen for the topography analysis. The ROI, of size 1800 x 2500 pixels where each pixel represents 2um, was repeatably measured. We show the sensitivity based on measurements and the comparison between center and edge die measurements. The topography measurements and surface patch analysis were applied to hundreds of images representing the periodic process qualification runs required to control and verify CMP performance and tool matching. The analysis is shown to be sensitive to process conditions that vary in polishing time, type of slurry, CMP tool manufacturer, and CMP pad lifetime. Keywords: Keywords: CMP, Topography, Image Processing, Metrology, Interference microscopy, surface processing [1] De Lega, Xavier Colonna, and Peter De Groot. "Optical topography measurement of patterned wafers." Characterization and Metrology for ULSI Technology 2005 788 (2005): 432-436. [2] de Groot, Peter. "Coherence scanning interferometry." Optical Measurement of Surface Topography. Springer Berlin Heidelberg, 2011. 187-208. [3] Watson, Layne T., Thomas J. Laffey, and Robert M. Haralick. "Topographic classification of digital image intensity surfaces using generalized splines and the discrete cosine transformation." Computer Vision, Graphics, and Image Processing 29.2 (1985): 143-167. [4] Wang, Jun, et al. "3D facial expression recognition based on primitive surface feature distribution." Computer Vision and Pattern Recognition, 2006 IEEE Computer Society Conference on. Vol. 2. IEEE, 2006.

Development of a surface topography instrument for automotive textured steel plate

NASA Astrophysics Data System (ADS)

Wang, Zhen; Wang, Shenghuai; Chen, Yurong; Xie, Tiebang

2010-08-01

The surface topography of automotive steel plate is decisive to its stamping, painting and image clarity performances. For measuring this kind of surface topography, an instrument has been developed based on the principle of vertical scanning white light microscopy interference principle. The microscopy interference system of this instrument is designed based on the structure of Linnik interference microscopy. The 1D worktable of Z direction is designed and introduced in details. The work principle of this instrument is analyzed. In measuring process, the interference microscopy is derived as a whole and the measured surface is scanned in vertical direction. The measurement accuracy and validity is verified by templates. Surface topography of textured steel plate is also measured by this instrument.

Effect of EDTA and phosphoric Acid pretreatment on the bonding effectiveness of self-etch adhesives to ground enamel.

PubMed

Ibrahim, Ihab M; Elkassas, Dina W; Yousry, Mai M

2010-10-01

This in vitro study determined the effect of enamel pretreatment with phosphoric acid and ethylenediaminetetraacetic acid (EDTA) on the bond strength of strong, intermediary strong, and mild self-etching adhesive systems. Ninety sound human premolars were used. Resin composite cylinders were bonded to flat ground enamel surfaces using three self-etching adhesive systems: strong Adper Prompt L-Pop (pH=0.9-1.0), intermediary strong AdheSE (pH=1.6-1.7), and mild Frog (pH=2). Adhesive systems were applied either according to manufacturer instructions (control) or after pretreatment with either phosphoric acid or EDTA (n=10). After 24 hours, shear bond strength was tested using a universal testing machine at a cross-head speed of 0.5 mm/minute. Ultra-morphological characterization of the surface topography and resin/enamel interfaces as well as representative fractured enamel specimens were examined using scanning electron microscopy (SEM). Neither surface pretreatment statistically increased the mean shear bond strength values of either the strong or the intermediary strong self-etching adhesive systems. However, phosphoric acid pretreatment significantly increased the mean shear bond strength values of the mild self-etching adhesive system. SEM examination of enamel surface topography showed that phosphoric acid pretreatment deepened the same etching pattern of the strong and intermediary strong adhesive systems but converted the irregular etching pattern of the mild self-etching adhesive system to a regular etching pattern. SEM examination of the resin/enamel interface revealed that deepening of the etching pattern was consistent with increase in the length of resin tags. EDTA pretreatment had a negligible effect on ultra-morphological features. Use of phosphoric acid pretreatment can be beneficial with mild self-etching adhesive systems for bonding to enamel.

Effect of EDTA and Phosphoric Acid Pretreatment on the Bonding Effectiveness of Self-Etch Adhesives to Ground Enamel

PubMed Central

Ibrahim, Ihab M.; Elkassas, Dina W.; Yousry, Mai M.

2010-01-01

Objectives: This in vitro study determined the effect of enamel pretreatment with phosphoric acid and ethylenediaminetetraacetic acid (EDTA) on the bond strength of strong, intermediary strong, and mild self-etching adhesive systems. Methods: Ninety sound human premolars were used. Resin composite cylinders were bonded to flat ground enamel surfaces using three self-etching adhesive systems: strong Adper Prompt L-Pop (pH=0.9–1.0), intermediary strong AdheSE (pH=1.6–1.7), and mild Frog (pH=2). Adhesive systems were applied either according to manufacturer instructions (control) or after pretreatment with either phosphoric acid or EDTA (n=10). After 24 hours, shear bond strength was tested using a universal testing machine at a cross-head speed of 0.5 mm/minute. Ultra-morphological characterization of the surface topography and resin/enamel interfaces as well as representative fractured enamel specimens were examined using scanning electron microscopy (SEM). Results: Neither surface pretreatment statistically increased the mean shear bond strength values of either the strong or the intermediary strong self-etching adhesive systems. However, phosphoric acid pretreatment significantly increased the mean shear bond strength values of the mild self-etching adhesive system. SEM examination of enamel surface topography showed that phosphoric acid pretreatment deepened the same etching pattern of the strong and intermediary strong adhesive systems but converted the irregular etching pattern of the mild self-etching adhesive system to a regular etching pattern. SEM examination of the resin/enamel interface revealed that deepening of the etching pattern was consistent with increase in the length of resin tags. EDTA pretreatment had a negligible effect on ultra-morphological features. Conclusions: Use of phosphoric acid pretreatment can be beneficial with mild self-etching adhesive systems for bonding to enamel. PMID:20922162

Velopharyngeal mucosal surface topography in healthy subjects and subjects with obstructive sleep apnea.

PubMed

Lambeth, Christopher; Amatoury, Jason; Wang, Ziyu; Foster, Sheryl; Amis, Terence; Kairaitis, Kristina

2017-03-01

Macroscopic pharyngeal anatomical abnormalities are thought to contribute to the pathogenesis of upper airway (UA) obstruction in obstructive sleep apnea (OSA). Microscopic changes in the UA mucosal lining of OSA subjects are reported; however, the impact of these changes on UA mucosal surface topography is unknown. This study aimed to 1 ) develop methodology to measure UA mucosal surface topography, and 2 ) compare findings from healthy and OSA subjects. Ten healthy and eleven OSA subjects were studied. Awake, gated (end expiration), head and neck position controlled magnetic resonance images (MRIs) of the velopharynx (VP) were obtained. VP mucosal surfaces were segmented from axial images, and three-dimensional VP mucosal surface models were constructed. Curvature analysis of the models was used to study the VP mucosal surface topography. Principal, mean, and Gaussian curvatures were used to define surface shape composition and surface roughness of the VP mucosal surface models. Significant differences were found in the surface shape composition, with more saddle/spherical and less flat/cylindrical shapes in OSA than healthy VP mucosal surface models ( P < 0.01). OSA VP mucosal surface models were also found to have more mucosal surface roughness ( P < 0.0001) than healthy VP mucosal surface models. Our novel methodology was utilized to model the VP mucosal surface of OSA and healthy subjects. OSA subjects were found to have different VP mucosal surface topography, composed of increased irregular shapes and increased roughness. We speculate increased irregularity in VP mucosal surface may increase pharyngeal collapsibility as a consequence of friction-related pressure loss. NEW & NOTEWORTHY A new methodology was used to model the upper airway mucosal surface topography from magnetic resonance images of patients with obstructive sleep apnea and healthy adults. Curvature analysis was used to analyze the topography of the models, and a new metric was derived to describe the mucosal surface roughness. Increased roughness was found in the obstructive sleep apnea vs. healthy group, but further research is required to determine the functional effects of the measured difference on upper airway airflow mechanics. Copyright © 2017 the American Physiological Society.

Effects of titanium surface topography on bone integration: a systematic review.

PubMed

Wennerberg, Ann; Albrektsson, Tomas

2009-09-01

To analyse possible effects of titanium surface topography on bone integration. Our analyses were centred on a PubMed search that identified 1184 publications of assumed relevance; of those, 1064 had to be disregarded because they did not accurately present in vivo data on bone response to surface topography. The remaining 120 papers were read and analysed, after removal of an additional 20 papers that mainly dealt with CaP-coated and Zr implants; 100 papers remained and formed the basis for this paper. The bone response to differently configurated surfaces was mainly evaluated by histomorphometry (bone-to-implant contact), removal torque and pushout/pullout tests. A huge number of the experimental investigations have demonstrated that the bone response was influenced by the implant surface topography; smooth (S(a)<0.5 microm) and minimally rough (S(a) 0.5-1 mum) surfaces showed less strong bone responses than rougher surfaces. Moderately rough (S(a)>1-2 microm) surfaces showed stronger bone responses than rough (S(a)>2 microm) in some studies. One limitation was that it was difficult to compare many studies because of the varying quality of surface evaluations; a surface termed 'rough' in one study was not uncommonly referred to as 'smooth' in another; many investigators falsely assumed that surface preparation per se identified the roughness of the implant; and many other studies used only qualitative techniques such as SEM. Furthermore, filtering techniques differed or only height parameters (S(a), R(a)) were reported. * Surface topography influences bone response at the micrometre level. * Some indications exist that surface topography influences bone response at the nanometre level. * The majority of published papers present an inadequate surface characterization. * Measurement and evaluation techniques need to be standardized. * Not only height descriptive parameters but also spatial and hybrid ones should be used.

Bacterial resistance of self-assembled surfaces using PPOm-b-PSBMAn zwitterionic copolymer - concomitant effects of surface topography and surface chemistry on attachment of live bacteria.

PubMed

Hsiao, Sheng-Wen; Venault, Antoine; Yang, Hui-Shan; Chang, Yung

2014-06-01

Three well-defined diblock copolymers made of poly(sulfobetaine methacrylate) (poly(SBMA)) and poly(propylene oxide) (PPO) groups were synthesized by atom transfer radical polymerization (ATRP) method. They were physically adsorbed onto three types of surfaces having different topography, including smooth flat surface, convex surface, and indented surface. Chemical state of surfaces was characterized by XPS while the various topographies were examined by SEM and AFM. Hydrophilicity of surfaces was dependent on both the surface chemistry and the surface topography, suggesting that orientation of copolymer brushes can be tuned in the design of surfaces aimed at resisting bacterial attachment. Escherichia coli, Staphylococcus epidermidis, Streptococcus mutans and Escherichia coli with green fluorescent protein (E. coli GFP) were used in bacterial tests to assess the resistance to bacterial attachment of poly(SBMA)-covered surfaces. Results highlighted a drastic improvement of resistance to bacterial adhesion with the increasing of poly(SBMA) to PPO ratio, as well as an important effect of surface topography. The chemical effect was directly related to the length of the hydrophilic moieties. When longer, more water could be entrapped, leading to improved anti-bacterial properties. The physical effect impacted on the orientation of the copolymer brushes, as well as on the surface contact area available. Convex surfaces as well as indented surfaces wafer presented the best resistance to bacterial adhesion. Indeed, bacterial attachment was more importantly reduced on these surfaces compared with smooth surfaces. It was explained by the non-orthogonal orientation of copolymer brushes, resulting in a more efficient surface coverage of zwitterionic molecules. This work suggests that not only the control of surface chemistry is essential in the preparation of surfaces resisting bacterial attachment, but also the control of surface topography and orientation of antifouling moieties. Copyright © 2014 Elsevier B.V. All rights reserved.

Measuring surface topography with scanning electron microscopy. I. EZEImage: a program to obtain 3D surface data.

PubMed

Ponz, Ezequiel; Ladaga, Juan Luis; Bonetto, Rita Dominga

2006-04-01

Scanning electron microscopy (SEM) is widely used in the science of materials and different parameters were developed to characterize the surface roughness. In a previous work, we studied the surface topography with fractal dimension at low scale and two parameters at high scale by using the variogram, that is, variance vs. step log-log graph, of a SEM image. Those studies were carried out with the FERImage program, previously developed by us. To verify the previously accepted hypothesis by working with only an image, it is indispensable to have reliable three-dimensional (3D) surface data. In this work, a new program (EZEImage) to characterize 3D surface topography in SEM has been developed. It uses fast cross correlation and dynamic programming to obtain reliable dense height maps in a few seconds which can be displayed as an image where each gray level represents a height value. This image can be used for the FERImage program or any other software to obtain surface topography characteristics. EZEImage also generates anaglyph images as well as characterizes 3D surface topography by means of a parameter set to describe amplitude properties and three functional indices for characterizing bearing and fluid properties.

Importance of Including Topography in Numerical Simulations of Venus' Atmospheric Circulation

NASA Astrophysics Data System (ADS)

Parish, H. F.; Schubert, G.; Lebonnois, S.; Covey, C. C.; Walterscheid, R. L.; Grossman, A.

2012-12-01

Venus' atmosphere is characterized by strong superrotation, in which the wind velocities at cloud heights are around 60 times faster than the surface rotation rate. The reasons for this strong superrotation are still not well understood. Since the surface of the planet is both a source and sink of atmospheric angular momentum it is important to understand and properly account for the interactions at the surface-atmosphere boundary. A key aspect of the surface-atmosphere interaction is the topography. Topography has been introduced into different general circulation models (GCMs) of Venus' atmosphere, producing significant, but widely varying effects on the atmospheric circulation. The reasons for the inconsistencies among model results are not well known, but our studies suggest they might be related to the influences of different dynamical cores. In our recent study, we have analyzed the angular momentum budget for two Venus GCMs, the Venus Community Atmosphere model (Venus CAM) and the Laboratoire de Meteorologie Dynamique (LMD) Venus GCM. Because of Venus' low magnitude surface winds, surface friction alone supplies only a relatively weak angular momentum forcing to the atmosphere. We find that if surface friction is introduced without including surface topography, the angular momentum balance of the atmosphere may be dominated by effects such as numerical diffusion, a sponge layer, or other numerical residuals that are generally included in all GCMs, and can themselves be sources of angular momentum. However, we find the mountain torque associated with realistic Venus surface topography supplies a much larger source of angular momentum than the surface friction, and dominates nonphysical numerical terms. (A similar effect occurs for rapidly rotating planets like Earth, but in this case numerical errors in the angular momentum budget are relatively small even in the absence of mountain torque). Even if surface friction dominates numerical terms in the angular momentum budgets of simulations without realistic topography, it must be remembered that there are no observational constraints on model parameterizations of the real surface friction on Venus. It is essential for a planet such as Venus, for which surface friction alone supplies only weak angular momentum forcing, to include surface topography to generate realistic forcing of angular momentum and avoid the influences of numerical artifacts, which can be significant. Venus' topography, as mapped using measurements from the Magellan mission, shows significant hemispheric asymmetry. In this work we examine the impact of this asymmetry using simulations of Venus' circulation with and without topography, within the latest version of the Venus CAM GCM.

Constraints on Lithospheric Rheology from Observations of Coronae on Venus

NASA Astrophysics Data System (ADS)

O'Rourke, Joseph G.; Smrekar, Suzanne; Moresi, Louis N.

2016-10-01

Coronae are enigmatic, quasi-circular features found in myriad geological environments. They are primarily distinguished as rings of concentric fractures superimposed on various topographic profiles with at least small-scale volcanism. Mantle plumes may produce coronae with interior rises, whereas coronae with central depressions are often attributed to downwellings like Rayleigh-Taylor instabilities. For almost three decades, modelers have attempted to reproduce the topographic and gravity profiles measured at coronae. Until recently, few studies also considered tectonic deformation and melt production. In particular, "Type 2" coronae have complete topographic rims but arcs of fractures extending less than 180°, signifying both brittle and ductile deformation. Only a narrow range of rheological parameters like temperature and volatile content may be compatible with these observations. Ultimately, identifying how lithospheric properties differ between Earth and Venus is critical to understanding what factors permit plate tectonics on rocky, Earth-sized planets.Here we present a hierarchical approach to study the formation of coronae. First, we discuss an observational survey enabled by a new digital elevation model derived from stereo topography for ~20% of the surface of Venus, which offers an order-of-magnitude improvement over the horizontal resolution (10 to 20 kilometers) of altimetry data from NASA's Magellan mission. Next, we search this new dataset for signs of lithospheric flexure around small coronae. Simple, thin-elastic plate models were fit to topographic profiles of larger coronae in previous studies, but data resolution impeded efforts to apply this method to the entire coronae population. Finally, we show simulations of the formation of coronae using Underworld II, an open-source code adaptable to a variety of geodynamical problems. We benchmark our code using models of pure Rayleigh-Taylor instabilities and then investigate the influence of realistic rheology and three-dimensional effects on the topography, tectonics, and magmatism.

Pleistocene vertical motions of the Costa Rican outer forearc from subducting topography and a migrating fracture zone triple junction

USGS Publications Warehouse

Edwards, Joel H.; Kluesner, Jared W.; Silver, Eli A.; Bangs, Nathan L.

2018-01-01

Understanding the links between subducting slabs and upper-plate deformation is a longstanding goal in the field of tectonics. New 3D seismic sequence stratigraphy, mapped within the Costa Rica Seismogenesis Project (CRISP) seismic-reflection volume offshore southern Costa Rica, spatiotemporally constrains several Pleistocene outer forearc processes and provides clearer connections to subducting plate dynamics. Three significant shelf and/or slope erosional events at ca. 2.5–2.3 Ma, 1.95–1.78 Ma, and 1.78–1.19 Ma, each with notable differences in spatial extent, volume removed, and subsequent margin response, caused abrupt shifts in sedimentation patterns and rates. These shifts, coupled with observed deformation, suggest three primary mechanisms for Pleistocene shelf and slope vertical motions: (1) regional subaerial erosion and rapid subsidence linked to the southeastward Panama Fracture Zone triple-junction migration, with associated abrupt bathymetric variations and plate kinematic changes; (2) transient, kilometer-scale uplift and subsidence due to inferred subducting plate topography; and (3) progressive outer wedge shortening accommodated by landward- and seaward-dipping thrust faults and fold development due to the impinging Cocos Ridge. Furthermore, we find that the present-day wedge geometry (to within ∼3 km along strike) has been maintained through the Pleistocene, in contrast to modeled landward margin retreat. We also observe that deformation, i.e., extension and shortening, is decoupled from net margin subsidence. Our findings do not require basal erosion, and they suggest that the vertical motions of the Costa Rican outer forearc are not the result of a particular continuous process, but rather are a summation of plate to plate changes (e.g., passage of a fracture zone triple junction) and episodic events (e.g., subducting plate topography).

A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hui Tian, Guilhem Ribeill, Chen Xu, Charles E. Reece, Michael J. Kelley

2011-03-01

As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. Amore » more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.« less

Spontaneous development of arcuate single-sided subduction in global 3-D mantle convection models with a free surface

NASA Astrophysics Data System (ADS)

Crameri, Fabio; Tackley, Paul

2014-05-01

The work presented aims at a better understanding of plate tectonics, a crucial dynamical feature within the global framework of mantle convection. Special focus is given to the interaction of subduction-related mantle flow and surface topography. Thereby, the application of a numerical model with two key functional requirements is essential: an evolution over a long time period to naturally model mantle flow and a physically correct topography calculation. The global mantle convection model presented in Crameri et al. (2012a) satisfies both of these requirements. First, it is efficiently calculated by the finite-volume code Stag-YY (e.g., Tackley 2008) using a multi-grid method on a fully staggered grid. Second, it applies the sticky-air method (Matsumoto and Tomoda 1983; Schmeling et al, 2008) and thus approximates a free surface when the sticky-air parameters are chosen carefully (Crameri et al., 2012b). This leads to dynamically self-consistent mantle convection with realistic, single-sided subduction. New insights are thus gained into the interplay of obliquely sinking plates, toroidal mantle flow and the arcuate shape of slabs and trenches. Numerous two-dimensional experiments provide optimal parameter setups that are applied to three-dimensional models in Cartesian and fully spherical geometries. Features observed and characterised in the latter experiments give important insight into the strongly variable behaviour of subduction zones along their strike. This includes (i) the spontaneous development of arcuate trench geometry, (ii) regional subduction polarity reversals and slab tearing, and the newly discovered features (iii) 'slab tunnelling' and (iv) 'back-slab spiral flow'. Overall, this study demonstrates the strong interaction between surface topography and mantle currents and highlights the variability of subduction zones and their individual segments. REFERENCES Crameri, F., P. J. Tackley, I. Meilick, T. V. Gerya, and B. J. P. Kaus (2012a), A free plate surface and weak oceanic crust produce single-sided subduction on Earth, Geophys. Res. Lett., 39(3), L03,306. Crameri, F., H. Schmeling, G. J. Golabek, T. Duretz, R. Orendt, S. J. H. Buiter, D. A. May, B. J. P. Kaus, T. V. Gerya, and P. J. Tackley (2012b), A comparison of numerical surface topography calculations in geodynamic modelling: an evaluation of the 'sticky air' method, Geophys. J. Int., 189(1), 38-54. Matsumoto, T., and Y. Tomoda (1983), Numerical simulation of the initiation of subduction at the fracture zone, J. Phys. Earth, 31(3), 183-194. Schmeling, H., A. Babeyko, A. Enns, C. Faccenna, F. Funiciello, T. Gerya, G. Golabek, S. Grigull, B. Kaus, G. Morra, S. Schmalholz, and J. van Hunen (2008), A benchmark comparison of spontaneous subduction models-Towards a free surface, Phys. Earth Planet. Int., 171(1-4), 198-223. Tackley, P. J. (2008), Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid, Phys. Earth Planet. Int., 171(1-4), 7-18.

Sintered silver joints via controlled topography of electronic packaging subcomponents

DOEpatents

Wereszczak, Andrew A.

2014-09-02

Disclosed are sintered silver bonded electronic package subcomponents and methods for making the same. Embodiments of the sintered silver bonded EPSs include topography modification of one or more metal surfaces of semiconductor devices bonded together by the sintered silver joint. The sintered silver bonded EPSs include a first semiconductor device having a first metal surface, the first metal surface having a modified topography that has been chemically etched, grit blasted, uniaxial ground and/or grid sliced connected to a second semiconductor device which may also include a first metal surface with a modified topography, a silver plating layer on the first metal surface of the first semiconductor device and a silver plating layer on the first metal surface of the second semiconductor device and a sintered silver joint between the silver plating layers of the first and second semiconductor devices which bonds the first semiconductor device to the second semiconductor device.

Laser-based nanoengineering of surface topographies for biomedical applications

NASA Astrophysics Data System (ADS)

Schlie, Sabrina; Fadeeva, Elena; Koroleva, Anastasia; Ovsianikov, Aleksandr; Koch, Jürgen; Ngezahayo, Anaclet; Chichkov, Boris. N.

2011-04-01

In this study femtosecond laser systems were used for nanoengineering of special surface topographies in silicon and titanium. Besides the control of feature sizes, we demonstrated that laser structuring caused changes in material wettability due to a reduced surface contact area. These laser-engineered topographies were tested for their capability to control cellular behavior of human fibroblasts, SH-SY5Y neuroblastoma cells, and MG-63 osteoblasts. We found that fibroblasts reduced cell growth on the structures, while the other cell types proliferated at the same rate. These findings make laser-surface structuring very attractive for biomedical applications. Finally, to explain the results the correlation between topography and the biophysics of cellular adhesion, which is the key step of selective cell control, is discussed.

The Role of Titanium Surface Microtopography on Adhesion, Proliferation, Transformation, and Matrix Deposition of Corneal Cells.

PubMed

Zhou, Chengxin; Lei, Fengyang; Chodosh, James; Paschalis, Eleftherios I

2016-04-01

Titanium (Ti) is an excellent implantable biomaterial that can be further enhanced by surface topography optimization. Despite numerous data from orthopedics and dentistry, the effect of Ti surface topography on ocular cells is still poorly understood. In light of the recent adaptation of Ti in the Boston Keratoprosthesis artificial cornea, we attempted to perform an extended evaluation of the effect of Ti surface topography on corneal cell adhesion, proliferation, cytotoxicity, transformation, and matrix deposition. Different surface topographies were generated on medical grade Ti-6Al-4V-ELI (extra-low interstitial), with linearly increased roughness (polished to grit blasted). Biological response was evaluated in vitro using human corneal limbal epithelial (HCLE) cells, stromal fibroblasts (HCF), and endothelial cells (HCEnC). None of the Ti surface topographies caused cytotoxicity to any of the three corneal cell types. However, rough Ti surface inhibited HCLE and HCF cell adhesion and proliferation, while HCEnC proliferation was unaffected. Long-term experiments with HCF revealed that rough Ti surface with R(a) (the arithmetic average of the profile height from the mean line) ≥ 1.15 μm suppressed HCF focal adhesion kinase phosphorylation, changed fibroblast morphology, and caused less aligned and reduced deposition of collagen matrix as compared to smooth Ti (R(a) ≤ 0.08 μm). In the presence of transforming growth factor β1 (TGFβ1) stimulation, rough Ti inhibited alpha-smooth muscle actin (α-SMA) expression and collagen deposition, leading to decreased myofibroblast transformation and disorganization of the collagen fibrils as compared to smooth Ti. This study suggests that Ti surface topography regulates corneal cell behavior in a tissue-dependent manner that varies across the corneal strata. Contrary to the accepted paradigm, smooth surface topography can enhance cell adhesion and proliferation and increase matrix deposition by corneal cells.

Bactericidal effects of plasma-modified surface chemistry of silicon nanograss

NASA Astrophysics Data System (ADS)

Ostrikov, Kola; Macgregor-Ramiasa, Melanie; Cavallaro, Alex; (Ken Ostrikov, Kostya; Vasilev, Krasimir

2016-08-01

The surface chemistry and topography of biomaterials regulate the adhesion and growth of microorganisms in ways that are still poorly understood. Silicon nanograss structures prepared via inductively coupled plasma etching were coated with plasma deposited nanometer-thin polymeric films to produce substrates with controlled topography and defined surface chemistry. The influence of surface properties on Staphylococcus aureus proliferation is demonstrated and explained in terms of nanograss substrate wetting behaviour. With the combination of the nanograss topography; hydrophilic plasma polymer coatings enhanced antimicrobial activity while hydrophobic coatings reduced it. This study advances the understanding of the effects of surface wettability on the bactericidal properties of reactive nano-engineered surfaces.

Monitoring electrical properties for improving the lithological and hydrological characterization of landslides

NASA Astrophysics Data System (ADS)

Malet, J. P.; Gance, J.; Lajaunie, M.; Gallistl, J.; Denchik, N.; Flores Orozco, A.; Ottowitz, D.; Supper, R.; Sailhac, P.; Gautier, S.; Schmutz, M.

2017-12-01

Imaging water flows in landslides is of critical importance as the distribution of pore-fluid pressures controls the dynamics (acceleration, deceleration) of the material. Detecting and imaging water is a difficult task, not only because of the complex topography and the small dimensions of the geological structures, but also because the landslide material consists of unsaturated porous and heterogeneous fractured media, leading to multi-scale water-flow properties. Further, these properties can change in time, in relation to temperature, rainfall and biological forcings. Electrical properties are relevant proxies of the sub-surface hydrological properties. In order to image water in landslide bodies, we propose to combine multi-frequency electrical and electromagnetic measurements using campaigns or permanent instruments, and surface/boreole investigations, installed on several unstable slopes in France. To evaluate the information gained from electrical properties for different geological conditions, we discuss electrical and electro-magnetic imaging results for data collected at four different landslides located in France (Super-Sauze and La Valette in the South East Alps, Lodève lin the southern border of the Massif Central Massif, and Séchilienne in the North French Alps). Time-lapse electrical DC resistivity observations, complex electrical conductivity (conduction and polarization/chargeability) measured by IP imaging methods, and controlled-source electromagnetic (CS-AMT) methods are discussed. Imaging results demonstrate an improved lithological characterization of the landslide structures (delineation of the sliding planes, identification of the fractures, discrimination of clay lenses with enhanced resolution); further, water infiltration within the soil matrix and/or the fractures is discriminated allowing better modelling of the hydrological regime of the landslides at the slope scale. This research is conducted in the frame of the project HYDROSLIDE - Hydrogeophysical Monitoring of Clay-Rich Landslides funded by the Austrian Science Fund (FWF) and the French Research Agency (ANR).

Tectonic architecture through Landsat-7 ETM+/SRTM DEM-derived lineaments and relationship to the hydrogeologic setting in Siwa region, NW Egypt

NASA Astrophysics Data System (ADS)

Masoud, Alaa; Koike, Katsuaki

2006-08-01

Fracture zones on the Earth's surface are important elements in the understanding of plate motion forces, the dynamics of the subsurface fluid flow, and earthquake distributions. However, good exposures of these features are always lacking in arid regions, characterized by flat topography and where sand dunes extensively cover the terrain. During field surveys these conditions, in many cases, hinder the proper characterization of such features. Therefore, an approach that identifies the regional fractures as lineaments on remotely-sensed images or shaded digital terrain models, with its large scale synoptic coverage, could be promising. In the present work, a segment tracing algorithm (STA), for lineament detection from Landsat-7 Enhanced Thematic Mapper Plus (ETM+) imagery, and the data from the Shuttle Radar Topographic Mission (SRTM) 30 m digital elevation model (DEM), has been applied in the Siwa region, located in the northwest of the Western Desert of Egypt. The objectives are to analyze the spatial variation in orientation of the detected linear features and its relation to the hydrogeologic setting in the area and the underlying geology, and to evaluate the performance of the algorithm applied to the ETM+ and the DEM data. Detailed structural analysis and better understanding of the tectonic evolution of the area could provide useful tools for hydrologists for reliable groundwater management and development planning. The results obtained have been evaluated by the structural analysis of the area and field observations. Four major vertical fracture zones were detected corresponding to two conjugate sets of strike-slip faults that governed the surface, and subsurface environments of the lakes in the region, and these correlate well with the regional tectonics.

Measuring topographies from conventional SEM acquisitions.

PubMed

Shi, Qiwei; Roux, Stéphane; Latourte, Félix; Hild, François; Loisnard, Dominique; Brynaert, Nicolas

2018-04-27

The present study extends the stereoscopic imaging principle for estimating the surface topography to two orientations, namely, normal to the electron beam axis and inclined at 70° as suited for EBSD analyses. In spite of the large angle difference, it is shown that the topography can be accurately determined using regularized global Digital Image Correlation. The surface topography is compared to another estimate issued from a 3D FIB-SEM procedure where the sample surface is first covered by a Pt layer, and its initial topography is progressively revealed from successive FIB-milling. These two methods are successfully compared on a 6% strained steel specimen in an in situ mechanical test. This analysis is supplemented by a third approach estimating the change of topography from crystal rotations as measured from successive EBSD images. This last technique ignores plastic deformation, and thus only holds in an elastic regime. For the studied example, despite the large plastic flow, it is shown that crystal rotation already accounts for a significant part of the deformation-induced topography. Copyright © 2018 Elsevier B.V. All rights reserved.

Photographer : JPL Range : 225,000 kilometers (140,625 miles) This image of the Jovian moon Europa

NASA Technical Reports Server (NTRS)

1979-01-01

Photographer : JPL Range : 225,000 kilometers (140,625 miles) This image of the Jovian moon Europa was taken by Voyager 2 along the evening terminator, which best shows the surface topography of complex narrow ridges, seen as curved bright streaks, 5 to 10 kilometers wide, and typically 100 kilometers in length. The area shown is about 600 by 800 kilometers, and the smallest features visible are about 4 kilometers in size. Also visable are dark bands, more diffused in character, 20 to 40 kilometers wide and hundreds to thousands of kilometers in length. A few features are suggestive of impact craters but are rare, indication that the surface thought to be dominantly ice is still active, perhaps warmed by tidal heating like Io. The larger icy satellites, Callisto and Ganymede, are evidently colder with much more rigid crusts and ancient impact craters. The complex intersection of dark markings and bright ridges suggest that the surface has been fractured and material from beneath has welled up to fill the cracks.

A geologic analysis of the Side-Looking Airborne Radar imagery of southern New England

USGS Publications Warehouse

Banks, Paul T.

1975-01-01

Analysis of the side looking airborn radar imagery of Massachusetts, Connecticut and Rhode Island indicates that radar shows the topography in great detail. Since bedrock geologic features are frequently expressed in the topography the radar lends itself to geologic interpretation. The radar was studied by comparisons with field mapped geologic data first at a scale of approximately 1:125,000 and then at a scale of 1:500,000. The larger scale comparison revealed that faults, minor faults, joint sets, bedding and foliation attitudes, lithology and lithologic contacts all have a topographic expression interpretable on the imagery. Surficial geologic features were far less visible on the imagery over most of the area studied. The smaller scale comparisons revealed a pervasive, near orthogonal fracture set cutting all types and ages of rock and trending roughly N40?E and N30?W. In certain places the strike of bedding and foliation attitudes and some lithologic Contacts were visible in addition to the fractures. Fracturing in southern New England is apparently far more important than has been previously recognized. This new information, together with the visibility of many bedding and foliation attitudes and lithologic contacts, indicates the importance of radar imagery in improving the geologic interpretation of an area.

Chemical analyses (raw laboratory data) and locality index maps of the Confederate Gulch area, Broadwater and Meagher Counties, Montana

USGS Publications Warehouse

,

1975-01-01

Analysis of the side looking airborn radar imagery of Massachusetts, Connecticut and Rhode Island indicates that radar shows the topography in great detail. Since bedrock geologic features are frequently expressed in the topography the radar lends itself to geologic interpretation. The radar was studied by comparisons with field mapped geologic data first at a scale of approximately 1:125,000 and then at a scale of 1:500,000. The larger scale comparison revealed that faults, minor faults, joint sets, bedding and foliation attitudes, lithology and lithologic contacts all have a topographic expression interpretable on the imagery. Surficial geologic features were far less visible on the imagery over most of the area studied. The smaller scale comparisons revealed a pervasive, near orthogonal fracture set cutting all types and ages of rock and trending roughly N40?E and N30?W. In certain places the strike of bedding and foliation attitudes and some lithologic Contacts were visible in addition to the fractures. Fracturing in southern New England is apparently far more important than has been previously recognized. This new information, together with the visibility of many bedding and foliation attitudes and lithologic contacts, indicates the importance of radar imagery in improving the geologic interpretation of an area.

Impact of dissolution and carbonate precipitation on carbon storage in basalt

NASA Astrophysics Data System (ADS)

Wells, R. K.; Xiong, W.; Tadeoye, J.; Menefee, A.; Ellis, B. R.; Skemer, P. A.; Giammar, D.

2016-12-01

The spatial evolution of silicate mineral dissolution, carbonate precipitation, and the transport of fluids influence the viability of carbon storage in basalt reservoirs. Dissolution of natural basalt and subsequent carbonate precipitation in systems with different transport processes operating were characterized using static and flow-through (5 mL/hr) experiments at 50, 100, and 150 °C, and 100 bar CO2. Intact samples and cores with milled pathways that simulate fractures were tested. Spatial and mineralogical patterns in dissolution and precipitation were analyzed using optical and electron microscopy, microCT scanning, and surface roughness data. Precipitates and fluid chemistry were analyzed using Raman spectroscopy, SEM-EDS, and ICP-MS. Analysis of the bulk solution and surface topography suggests dissolution of olivine and pyroxene grains begins within hours of the start of the experiments. In flow-through experiments, total effluent cation concentrations reach a peak concentration within a few hours then drop towards a steady state within a few days. In static experiments, the initial rate of cation release is faster than it is after several weeks. In both cases Ca2+, Mg2+, and Fe2+ are the dominant cations in solution in the initial stages of reaction. Lower concentrations of Na2+, K+, and Al3+, and the preservation of feldspar and matrix grains after several weeks of reaction indicate the slow reactivity of these minerals. As the reaction progresses, the surface roughness increases steadily with cavities developing at the sites of olivine and pyroxene grains. Post-reaction analysis of basalt samples reacted at static conditions with milled pathways reveals that both siderite and amorphous silica precipitated within diffusion-limited zones as early as 4-6 weeks. Siderite abundance varies with distance along the pathway with the highest concentration of carbonates 1-2 cm below the fracture opening. Siderite precipitates are large enough to fill fracture opening 100 μm wide within 4-6 weeks.

Topography and surface energy dependent calcium phosphate formation on Sol-Gel derived TiO2 coatings.

PubMed

Järn, Mikael; Areva, Sami; Pore, Viljami; Peltonen, Jouko; Linden, Mika

2006-09-12

Heterogeneous nucleation and growth of calcium phosphate (CaP) on sol-gel derived TiO(2) coatings was investigated in terms of surface topography and surface energy. The topography of the coatings was derived from AFM measurements, while the surface energy was determined with contact angle measurements. The degree of precipitation was examined with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The precipitation of CaP was found to be dependent on both topography and surface energy. A high roughness value when combining the RMS roughness parameter S(q) with the number of local maxima per unit area parameter S(ds) enhances CaP formation. The hydrophilicity of the coating was also found to be of importance for CaP formation. We suggest that the water contact angle, which is a direct measure of the hydrophilicity of the surface, may be used to evaluate the surface energy dependent precipitation kinetics rather than using the often applied Lewis base parameter.

Effect of Micro- and Nanoscale Topography on the Adhesion of Bacterial Cells to Solid Surfaces

PubMed Central

Hsu, Lillian C.; Fang, Jean; Borca-Tasciuc, Diana A.; Worobo, Randy W.

2013-01-01

Attachment and biofilm formation by bacterial pathogens on surfaces in natural, industrial, and hospital settings lead to infections and illnesses and even death. Minimizing bacterial attachment to surfaces using controlled topography could reduce the spreading of pathogens and, thus, the incidence of illnesses and subsequent human and financial losses. In this context, the attachment of key microorganisms, including Escherichia coli, Listeria innocua, and Pseudomonas fluorescens, to silica and alumina surfaces with micron and nanoscale topography was investigated. The results suggest that orientation of the attached cells occurs preferentially such as to maximize their contact area with the surface. Moreover, the bacterial cells exhibited different morphologies, including different number and size of cellular appendages, depending on the topographical details of the surface to which they attached. This suggests that bacteria may utilize different mechanisms of attachment in response to surface topography. These results are important for the design of novel microbe-repellant materials. PMID:23416997

Facile synthesis of biphasic calcium phosphate microspheres with engineered surface topography for controlled delivery of drugs and proteins.

PubMed

Zarkesh, Ibrahim; Ghanian, Mohammad Hossein; Azami, Mahmoud; Bagheri, Fatemeh; Baharvand, Hossein; Mohammadi, Javad; Eslaminejad, Mohamadreza Baghaban

2017-09-01

Biphasic calcium phosphate (BCP) microspheres are of great interest due to their high stability and osteoinductive properties at specific compositions. However, the need for optimal performance at a unique composition limits their flexibility for tuning drug release by modulation of bulk properties and presents the question of engineering surface topography as an alternative. It is necessary to have a facile method to control surface topography at a defined bulk composition. Here, we have produced BCP microspheres with different surface topographies that have the capability to be used as tunable drug release systems. We synthesized calcium deficient hydroxyapatite (CDHA) microparticles by precipitating calcium and phosphate ions onto ethylenediaminetetraacetic acid (EDTA) templates. The morphology and surface topography of CDHA microparticles were controlled using process parameters, which governed nucleation and growth. These parameters included template concentration, heat rate, and stirring speed. Under low heat rate and static conditions, we could obtain spherical microparticles with long and short nanosheets on their surfaces at low and high EDTA concentrations, respectively. These nanostructured microspheres were subsequently crystallized by thermal treatment to produce EDTA-free BCP microspheres with intact morphology. These biocompatible BCP microspheres were highly effective in loading and prolonged release of both small molecule [dexamethasone (Dex)] and protein [bovine serum albumin (BSA)] models. This strategy has enabled us to control the surface topography of BCP microspheres at defined compositions and holds tremendous promise for drug delivery and tissue engineering applications. Copyright © 2017 Elsevier B.V. All rights reserved.

The Relationship of the MOLA Topography of Mars to the Mean Atmospheric Pressure

NASA Technical Reports Server (NTRS)

Smith, David E.; Zuber, Maria T.

1999-01-01

The MOLA topography of Mars is based on a new mean radius of the planet and new equipotential surface for the areoid. The mean atmospheric pressure surface of 6.1mbars that has been used in the past as a reference level for topography does not apply to the zero level of MOLA elevations. The MOLA mean radius of the planet is 3389508 meters and the mean equatorial radius is 339600 meters. The areoid of the zero level of the MOLA altimetry is defined to be the potential surface with the same potential as the mean equatorial radius. The MOLA topography differs from the USGS digital elevation data by approximately 1.6 km, with MOLA higher. The average pressure on the MOLA reference surface for Ls =0 is approximately 5.1 mbars and has been derived from occultation data obtained from the tracking of Viking, Mariner, and MGS spacecraft and interpolated with the aid of the Ames Mars GCM. The new topography and the new occultation data are providing a more reliable relationship between elevation and surface pressure.

Characterization of Discharge Areas of Radionuclides Originating From Nuclear Waste Repositories

NASA Astrophysics Data System (ADS)

Marklund, L.; Xu, S.; Worman, A.

2009-05-01

If leakages in nuclear waste repositories located in crystalline bedrock arise, radionuclides will reach the biosphere and cause a risk of radiological impact. The extent of the radiological impact depends on in which landscape elements the radionuclides emerge. In this study, we investigate if there are certain landscape elements that generally will act as discharge areas for radionuclides leaking from subsurface deposits. We also characterize the typical properties that distinguish these areas from others. In humid regions, landscape topography is the most important driving force for groundwater flow. Because groundwater is the main transporting agent for migrating radionuclides, the topography will determine the flowpaths of leaking radionuclides. How topography and heterogeneities in the subsurface affect the discharge distribution of the radionuclides is therefore an important scope of this study. To address these issues, we developed a 3-D transport model. Our analyses are based on site-specific data from two different areas in Sweden, Forsmark, Uppland, and Oskarshamn, Småland. The Swedish Nuclear Waste Management Company (SKB) has selected these two areas as candidate areas for a deep repository of nuclear waste and the areas are currently subject to site investigations. Our results suggest that there are hot-spots in the landscape i.e. areas with high probability of receiving large amounts of radionuclides from a leaking repository of nuclear waste. The hot-spots concentrate in the sea, streams, lakes and wetlands. All these elements are found at lower elevations in the landscape. This pattern is mostly determined by the landscape topography and the locations of fracture zones. There is a relationship between fracture zones and topography, and therefore the importance of the topography for the discharge area distribution is not contradicted by the heterogeneity in the bedrock. The varieties of landscape elements which have potential for receiving significant amounts of radionuclides are limited. To limit the radiological dose assessment, analyses should be focused to and more detailed in such landscape areas in which doses are expected to be high. Due to the similarities among deep groundwater discharge areas, one can make site-specific analyses of those areas, which have a broad applicability for migration of radionuclides originating from a nuclear waste repository.

The absolute dynamic ocean topography (ADOT)

NASA Astrophysics Data System (ADS)

Bosch, Wolfgang; Savcenko, Roman

The sea surface slopes relative to the geoid (an equipotential surface) basically carry the in-formation on the absolute velocity field of the surface circulation. Pure oceanographic models may remain unspecific with respect to the absolute level of the ocean topography. In contrast, the geodetic approach to estimate the ocean topography as difference between sea level and the geoid gives by definition an absolute dynamic ocean topography (ADOT). This approach requires, however, a consistent treatment of geoid and sea surface heights, the first being usually derived from a band limited spherical harmonic series of the Earth gravity field and the second observed with much higher spectral resolution by satellite altimetry. The present contribution shows a procedure for estimating the ADOT along the altimeter profiles, preserving as much sea surface height details as the consistency w.r.t. the geoid heights will allow. The consistent treatment at data gaps and the coast is particular demanding and solved by a filter correction. The ADOT profiles are inspected for their innocent properties towards the coast and compared to external estimates of the ocean topography or the velocity field of the surface circulation as derived, for example, by ARGO floats.

Nonlinear analysis and dynamic compensation of stylus scanning measurement with wide range

NASA Astrophysics Data System (ADS)

Hui, Heiyang; Liu, Xiaojun; Lu, Wenlong

2011-12-01

Surface topography is an important geometrical feature of a workpiece that influences its quality and functions such as friction, wearing, lubrication and sealing. Precision measurement of surface topography is fundamental for product quality characterizing and assurance. Stylus scanning technique is a widely used method for surface topography measurement, and it is also regarded as the international standard method for 2-D surface characterizing. Usually surface topography, including primary profile, waviness and roughness, can be measured precisely and efficiently by this method. However, by stylus scanning method to measure curved surface topography, the nonlinear error is unavoidable because of the difference of horizontal position of the actual measured point from given sampling point and the nonlinear transformation process from vertical displacement of the stylus tip to angle displacement of the stylus arm, and the error increases with the increasing of measuring range. In this paper, a wide range stylus scanning measurement system based on cylindrical grating interference principle is constructed, the originations of the nonlinear error are analyzed, the error model is established and a solution to decrease the nonlinear error is proposed, through which the error of the collected data is dynamically compensated.

The effect of asteroid topography on surface ablation deflection

NASA Astrophysics Data System (ADS)

McMahon, Jay W.; Scheeres, Daniel J.

2017-02-01

Ablation techniques for deflecting hazardous asteroids deposit energy into the asteroid's surface, causing an effective thrust on the asteroid as the ablating material leaves normal to the surface. Although it has long been recognized that surface topography plays an important role in determining the deflection capabilities, most studies to date have ignored this aspect of the model. This paper focuses on understanding the topography for real asteroid shapes, and how this topography can change the deflection performance of an ablation technique. The near Earth asteroids Golevka, Bennu, and Itokawa are used as the basis for this study, as all three have high-resolution shape models available. This paper shows that naive targeting of an ablation method without accounting for the surface topography can lower the deflection performance by up to 20% in the cases studied in terms of the amount of acceleration applied in the desired direction. If the ablation thrust level is assumed to be 100 N, as used elsewhere in the literature, this misapplication of thrust translates to tens of kilometers per year in decreased semimajor axis change. However, if the ablation method can freely target any visible point on the surface of the asteroid, almost all of this performance can be recovered.

How Escherichia coli lands and forms cell clusters on a surface: a new role of surface topography

PubMed Central

Gu, Huan; Chen, Aaron; Song, Xinran; Brasch, Megan E.; Henderson, James H.; Ren, Dacheng

2016-01-01

Bacterial response to surface topography during biofilm formation was studied using 5 μm tall line patterns of poly (dimethylsiloxane) (PDMS). Escherichia coli cells attached on top of protruding line patterns were found to align more perpendicularly to the orientation of line patterns when the pattern narrowed. Consistently, cell cluster formation per unit area on 5 μm wide line patterns was reduced by 14-fold compared to flat PDMS. Contrasting the reduced colony formation, cells attached on narrow patterns were longer and had higher transcriptional activities, suggesting that such unfavorable topography may present a stress to attached cells. Results of mutant studies indicate that flagellar motility is involved in the observed preference in cell orientation on narrow patterns, which was corroborated by the changes in cell rotation pattern before settling on different surface topographies. These findings led to a set of new design principles for creating antifouling topographies, which was validated using 10 μm tall hexagonal patterns. PMID:27412365

The Role of Interface Shape on the Impact Characteristics and Cranial Fracture Patterns Using the Immature Porcine Head Model,.

PubMed

Vaughan, Patrick E; Vogelsberg, Caitlin C M; Vollner, Jennifer M; Fenton, Todd W; Haut, Roger C

2016-09-01

The forensic literature suggests that when adolescents fall onto edged and pointed surfaces, depressed fractures can occur at low energy levels. This study documents impact biomechanics and fracture characteristics of infant porcine skulls dropped onto flat, curved, edged, and focal surfaces. Results showed that the energy needed for fracture initiation was nearly four times higher against a flat surface than against the other surfaces. While characteristic measures of fracture such as number and length of fractures did not vary with impact surface shape, the fracture patterns did depend on impact surface shape. While experimental impacts against the flat surface produced linear fractures initiating at sutural boundaries peripheral to the point of impact (POI), more focal impacts produced depressed fractures initiating at the POI. The study supported case-based forensic literature suggesting cranial fracture patterns depend on impact surface shape and that fracture initiation energy is lower for more focal impacts. © 2016 American Academy of Forensic Sciences.

A science plan for a comprehensive assessment of water supply in the region underlain by fractured rock in Maryland

USGS Publications Warehouse

Fleming, Brandon J.; Hammond, Patrick A.; Stranko, Scott A.; Duigon, Mark T.; Kasraei, Saeid

2012-01-01

The fractured rock region of Maryland, which includes land areas north and west of the Interstate 95 corridor, is the source of water supply for approximately 4.4 million Marylanders, or approximately 76 percent of the State's population. Whereas hundreds of thousands of residents rely on wells (both domestic and community), millions rely on surface-water sources. In this region, land use, geology, topography, water withdrawals, impoundments, and other factors affect water-flow characteristics. The unconfined groundwater systems are closely interconnected with rivers and streams, and are affected by seasonal and climatic variations. During droughts, groundwater levels drop, thereby decreasing well yields, and in some cases, wells have gone dry. Low ground-water levels contribute to reduced streamflows, which in turn, can lead to reduced habitat for aquatic life. Increased demand, over-allocation, population growth, and climate change can affect the future sustainability of water supplies in the region of Maryland underlain by fractured rock. In response to recommendations of the 2008 Advisory Committee on the Management and Protection of the State's Water Resources report, the Maryland Department of the Environment's Water Supply Program, the Maryland Geological Survey, the Maryland Department of Natural Resources, Monitoring and Non-Tidal Assessment (MANTA) Division, and the U.S. Geological Survey have developed a science plan for a comprehensive assessment that will provide new scientific information, new data analysis, and new tools for the State to better manage water resources in the fractured rock region of Maryland. The science plan lays out five goals for the comprehensive assessment: (1) develop tools for the improved management and investigation of groundwater and surface-water resources; (2) characterize factors affecting reliable yields of individual groundwater and surface-water supplies; (3) investigate impacts on nearby water withdrawal users caused by groundwater and surface-water withdrawals; (4) assess the role of streamflow and water withdrawals on the ecological integrity of streams; and (5) improve understanding of the distribution of water-quality conditions in fractured rock aquifers. To accomplish these goals, accurate data collection, review, and analysis are needed, including the study of "Research Watersheds" that can provide detailed information about the potential effects that climate change and water withdrawals may have on groundwater, streamflow, and aquatic life. The assessment planning started in 2009 and is being conducted with close interagency coordination. A Fractured Rock Aquifer Information System is currently (2012) undergoing initial development. Other major tasks that will be performed include the development of work plans for each science goal, the estimation of daily streamflow at ungaged streams, and the design and implementation of Research Watersheds. Finally, scenarios will be modeled to evaluate current water allocation permitting methodologies, investigate effects on nearby water withdrawal users caused by groundwater and surface-water withdrawals, and assess the potential impacts of climate change on water resources. Desktop and Web-based tools will be developed in order to meet the diverse research needs of the assessment. These tools, including the Fractured Rock Aquifer Information System will be continuously improved during the assessment to store relevant groundwater and surface-water data in spatially referenced databases, estimate streamflows, locate higher-yielding wells, estimate the impacts of withdrawals on nearby users, and assess the cumulative impacts of withdrawals on the aquatic resource. Tools will be developed to serve the needs of many audiences, including water resource managers, water suppliers, planners, policymakers, and other scientific investigators.

[Influence of different surface treatments on porcelain surface topography].

PubMed

Tai, Yinxia; Zhu, Xianchun; Sen, Yan; Liu, Chang; Zhang, Xian; Shi, Xueming

2013-02-01

To evaluate the influence of different surface treatments on porcelain surface topography. Metal ceramic prostheses in 6 groups were treated according to the different surface treatment methods, and the surface topography was observed through scanning electron microscope (SEM). Group A was the control one (untreated), group B was etched by 9.6% hydrofluoric acid(HF), group C was deglazed by grinding and then etched by 9.6% HF, group D was treated with Nd: YAG laser irradiation(0.75 W) and HF etching, group E was treated with Nd: YAG laser irradiation (1.05 W) and HF etching, and group F was treated with laser irradiation (1.45 W) and HF etching. Surface topography was different in different groups. A lot of inerratic cracks with the shapes of rhombuses and grid, and crater with a shape of circle were observed on the ceramic surface after treatment with energy parameters of 1.05 W Nd: YAG laser irradiation and 9.6% HF etching (group E). Surface topography showed a lot of concaves on the inner wall of the cracks, and the concaves with diameter of 1-5 microm could be observed on the inner wall of the holes, which had a diameter of 20 microm under SEM. The use of Nd: YAG laser irradiation with the energy parameters of 1.05 W and the HF with a concentration of 9.6% can evenly coarsen the porcelain surface, that is an effective surface treatment method.

Can weak crust explain the correlation of geoid and topography on Venus?

NASA Technical Reports Server (NTRS)

Buck, W. Roger

1993-01-01

The effect on geoid and topography of low viscosity crust overlying a steady-state convecting mantle is estimated under the assumption that the shear between crust and mantle does not alter the mantle flow. The weak crustal layer can change the sign of the geoid to topography ratio (admittance). The positive long wavelength admittance for Venus is consistent with a weak crust overlying a mantle with a viscosity that increases strongly with depth. The accepted interpretation of the strong positive correlation of geoid and topography on Venus, is that the convecting mantle of Venus has a constant viscosity with depth. Topography results from vertical normal stresses caused by mantle convection and highlands occur where mantle upwells. For topography to be supported by normal stress, the time scale for crustal flow must be long compared to the time scale for changes in the pattern of mantle flow. Because the high surface temperature of Venus may cause the crust to have a low viscosity, this assumption may be false. Topography should then be dominated by shear coupling between the crust and mantle. In the absence of a crustal layer, convection in a constant viscosity layer gives rise to a geoid anomaly that correlates positively with surface topography. When the viscosity in the layer increases with depth by several orders of magnitude, the surface topography and geoid anomaly become anti-correlated.

Experimental and Numerical Study of the Influence of Substrate Surface Preparation on Adhesion Mechanisms of Aluminum Cold Spray Coatings on 300M Steel Substrates

NASA Astrophysics Data System (ADS)

Nastic, A.; Vijay, M.; Tieu, A.; Rahmati, S.; Jodoin, B.

2017-10-01

The effect of substrate surface topography on the creation of metallurgical bonds and mechanical anchoring points has been studied for the cold spray deposition of pure aluminum on 300M steel substrate material. The coatings adhesion strength showed a significant decrease from 31.0 ± 5.7 MPa on polished substrates to 6.9 ± 2.0 MPa for substrates with roughness of 2.2 ± 0.5 μm. Strengths in the vicinity of 45 MPa were reached for coatings deposited onto forced pulsed waterjet treated surfaces with roughnesses larger than 33.8 μm. Finite element analysis has confirmed the sole presence of mechanical anchoring in coating adhesion strength for all surface treatment except polished surfaces. Grit embedment has been shown to be non-detrimental to coating adhesion for the current deposited material combination. The particle deformation process during impacts has been studied through finite element analysis using the Preston-Tonks-Wallace (PTW) constitutive model. The obtained equivalent plastic strain (PEEQ), temperature, contact pressure and velocity vector were correlated to the particle ability to form metallurgical bonds. Favorable conditions for metallurgical bonding were found to be highest for particles deposited on polished substrates, as confirmed by fracture surface analysis.

The unique radar scattering properties of silicic lava flows and domes

NASA Technical Reports Server (NTRS)

Plaut, Jeffrey J.; Stofan, Ellen R.; Anderson, Steven W.; Crown, David A.

1995-01-01

Silicic (silica-rich) lava flows, such as rhyolite, rhyodacite, and dacite, possess unique physical properties primarily because of the relatively high viscosity of the molten lava. Silicic flows tend to be thicker than basaltic flows, and the resulting large-scale morphology is typically a steep-sided dome or flow lobe, with aspect ratios (height/length) sometimes approaching unity. The upper surfaces of silicic domes and flows are normally emplaced as relatively cool, brittle slabs that fracture as they are extruded from the central vent areas, and are then rafted away toward the flow margin as a brittle carapace above a more ductile interior layer. This mode of emplacement results in a surface with unique roughness characteristics, which can be well-characterized by multiparameter synthetic aperture radar (SAR) observations. In this paper, we examine the scattering properties of several silicic domes in the Inyo volcanic chain in the Eastern Sierra of California, using AIRSAR and TOPSAR data. Field measurements of intermediate-scale (cm to tens of m) surface topography and block size are used to assess the mechanisms of the scattering process, and to quantify the unique roughness characteristics of the flow surfaces.

Modeling Groundwater Flow System of a Drainage Basin in the Basement Complex Environment of Southwestern Nigera

NASA Astrophysics Data System (ADS)

Akinwumiju, Akinola S.; Olorunfemi, Martins O.

2018-05-01

This study attempted to model the groundwater flow system of a drainage basin within the Basement Complex environment of Southwestern Nigeria. Four groundwater models were derived from Vertical Electrical Sounding (VES) Data, remotely sensed data, geological information (hydrolineaments and lithology) and borehole data. Subsequently, two sub-surface (local and regional) flow systems were delineated in the study area. While the local flow system is controlled by surface topography, the regional flow system is controlled by the networks of intermediate and deep seated faults/fractures. The local flow system is characterized by convergence, divergence, inflow and outflow in places, while the regional flow system is dominated by NNE-SSW and W-E flow directions. Minor flow directions include NNW-SSE and E-W with possible linkages to the main flow-paths. The NNE-SSW regional flow system is a double open ended flow system with possible linkage to the Niger Trough. The W-E regional flow system is a single open ended system that originates within the study area (with possible linkage to the NNE-SSW regional flow system) and extends to Ikogosi in the adjoining drainage basin. Thus, the groundwater drainage basin of the study area is much larger and extensive than its surface drainage basin. The all year round flowing (perennial) rivers are linked to groundwater outcrops from faults/fractures and contact zones. Consequently, larger percentage of annual rainwater usually leaves the basin in form of runoff and base flow. Therefore, the basin is categorized as a donor basin but with suspected subsurface water input at its northeastern axis.

Feature-based characterisation of signature topography in laser powder bed fusion of metals

NASA Astrophysics Data System (ADS)

Senin, Nicola; Thompson, Adam; Leach, Richard

2018-04-01

The use of state-of-the-art areal topography measurement instrumentation allows for a high level of detail in the acquisition of topographic information at micrometric scales. The 3D geometric models of surface topography obtained from measured data create new opportunities for the investigation of manufacturing processes through characterisation of the surfaces of manufactured parts. Conventional methods for quantitative assessment of topography usually only involve the computation of texture parameters, summary indicators of topography-related characteristics that are computed over the investigated area. However, further useful information may be obtained through characterisation of signature topographic formations, as more direct indicators of manufacturing process behaviour and performance. In this work, laser powder bed fusion of metals is considered. An original algorithmic method is proposed to isolate relevant topographic formations and to quantify their dimensional and geometric properties, using areal topography data acquired by state-of-the-art areal topography measurement instrumentation.

Experimental study on infrared radiation temperature field of concrete under uniaxial compression

NASA Astrophysics Data System (ADS)

Lou, Quan; He, Xueqiu

2018-05-01

Infrared thermography, as a nondestructive, non-contact and real-time monitoring method, has great significance in assessing the stability of concrete structure and monitoring its failure. It is necessary to conduct in depth study on the mechanism and application of infrared radiation (IR) of concrete failure under loading. In this paper, the concrete specimens with size of 100 × 100 × 100 mm were adopted to carry out the uniaxial compressions for the IR tests. The distribution of IR temperatures (IRTs), surface topography of IRT field and the reconstructed IR images were studied. The results show that the IRT distribution follows the Gaussian distribution, and the R2 of Gaussian fitting changes along with the loading time. The abnormities of R2 and AE counts display the opposite variation trends. The surface topography of IRT field is similar to the hyperbolic paraboloid, which is related to the stress distribution in the sample. The R2 of hyperbolic paraboloid fitting presents an upward trend prior to the fracture which enables to change the IRT field significantly. This R2 has a sharp drop in response to this large destruction. The normalization images of IRT field, including the row and column normalization images, were proposed as auxiliary means to analyze the IRT field. The row and column normalization images respectively show the transverse and longitudinal distribution of the IRT field, and they have clear responses to the destruction occurring on the sample surface. In this paper, the new methods and quantitative index were proposed for the analysis of IRT field, which have some theoretical and instructive significance for the analysis of the characteristics of IRT field, as well as the monitoring of instability and failure for concrete structure.

The evolution of fracture surface roughness and its dependence on slip

NASA Astrophysics Data System (ADS)

Wells, Olivia L.

Under effective compression, impingement of opposing rough surfaces of a fracture can force the walls of the fracture apart during slip. Therefore, a fracture's surface roughness exerts a primary control on the amount of dilation that can be sustained on a fracture since the opposing surfaces need to remain in contact. Previous work has attempted to characterize fracture surface roughness through topographic profiles and power spectral density analysis, but these metrics describing the geometry of a fracture's surface are often non-unique when used independently. However, when combined these metrics are affective at characterizing fracture surface roughness, as well as the mechanisms affecting changes in roughness with increasing slip, and therefore changes in dilation. These mechanisms include the influence of primary grains and pores on initial fracture roughness, the effect of linkage on locally increasing roughness, and asperity destruction that limits the heights of asperities and forms gouge. This analysis reveals four essential stages of dilation during the lifecycle of a natural fracture, whereas previous slip-dilation models do not adequately address the evolution of fracture surface roughness: (1) initial slip companied by small dilation is mediated by roughness controlled by the primary grain and pore dimensions; (2) rapid dilation during and immediately following fracture growth by linkage of formerly isolated fractures; (3) wear of the fracture surface and gouge formation that minimizes dilation; and (4) between slip events cementation that modifies the mineral constituents in the fracture. By identifying these fundamental mechanisms that influence fracture surface roughness, this new conceptual model relating dilation to slip has specific applications to Enhanced Geothermal Systems (EGS), which attempt to produce long-lived dilation in natural fractures by inducing slip.

Cell adhesion on nanotopography

NASA Astrophysics Data System (ADS)

Tsai, Irene; Kimura, Masahiro; Stockton, Rebecca; Jacobson, Bruce; Russell, Thomas

2003-03-01

Cell adhesion, a key element in understanding the cell-biomaterial interactions, underpins proper cell growth, function and survival. Understanding the parameters influencing cell adhesion is critical for applications in biosensors, implants and bioreactors. A gradient surface is used to study the effect of the surface topography on cell adhesion. A gradient surface is generated by block copolymer and homopolymer blends. The two homopolymers will phase separate on the micron scale and gradually decrease to nano-scale by the microphase separation of the diblock. Gradient surfaces offer a unique opportunity to probe lateral variations in the topography and interactions. Using thin films of mixtures of diblock copolymers of PS-b-MMA with PS and PMMA homopolymers, where the concentration of the PS-b-MMA varies across the surface, a gradient in the size scale of the morphology, from the nanoscopic to microscopic, was produced. By UV exposure, the variation in morphology translated into a variation in topography. The extent of cell spreading and cytoskeleton formation was investigated and marked dependence on the length scale of the surface topography was found.

Macrophage responses to 316L stainless steel and cobalt chromium alloys with different surface topographies.

PubMed

Anderson, Jordan A; Lamichhane, Sujan; Mani, Gopinath

2016-11-01

The surface topography of a biomaterial plays a vital role in determining macrophage interactions and influencing immune response. In this study, we investigated the effect of smooth and microrough topographies of commonly used metallic biomaterials such as 316 L stainless steel (SS) and cobalt-chromium (CoCr) alloys on macrophage interactions. The macrophage adhesion was greater on CoCr compared to SS, irrespective of their topographies. The macrophage activation and the secretion of most pro-inflammatory cytokines (TNF-α, IL-6, and IP-10) were greater on microrough surfaces than on smooth surfaces by day-1. However, by day-2, the macrophage activation on smooth surfaces was also significantly increased up to the same level as observed on the microrough surfaces, with more amount of cytokines secreted. The secretion of anti-inflammatory cytokine (IL-10) was significantly increased from day-1 to day-2 on all the alloy surfaces with the effect most prominently observed on microrough surfaces. The production of nitric oxide by the macrophages did not show any major substrate-dependent effect. The foreign body giant cells formed by macrophages were least observed on the microrough surfaces of CoCr. Thus, this study demonstrated that the nature of material (SS or CoCr) and their surface topographies (smooth or microrough) strongly influence the macrophage responses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2658-2672, 2016. © 2016 Wiley Periodicals, Inc.

Simulation of Cavern Formation and Karst Development Using Salt

ERIC Educational Resources Information Center

Kent, Douglas C.; Ross, Alex R.

1975-01-01

A salt model was developed as a teaching tool to demonstrate the development of caverns and karst topography. Salt slabs are placed in a watertight box to represent fractured limestone. Erosion resulting from water flow can be photographed in time-lapse sequence or demonstrated in the laboratory. (Author/CP)

Patterning of novel breast implant surfaces by enhancing silicone biocompatibility, using biomimetic topographies.

PubMed

Barr, S; Hill, E; Bayat, A

2010-04-26

Silicone biocompatibility is dictated by cell-surface interaction and its understanding is important in the field of implantation. The role of surface topography and its associated cellular morphology needs investigation to identify qualities that enhance silicone surface biocompatability. This study aims to create well-defined silicone topographies and examine how breast tissue-derived fibroblasts react and align to these surfaces. Photolithographic microelectronic techniques were modified to produce naturally inspired topographies in silicone, which were cultured with breast tissue-derived human fibroblasts. Using light, immunofluorescent and atomic force microscopy, the cytoskeletal reaction of fibroblasts to these silicone surfaces was investigated. Numerous, well-defined micron-sized pillars, pores, grooves, and ridges were manufactured and characterized in medical grade silicone. Inimitable immunofluorescent microscopy represented in our high magnification images of vinculin, vimentin, and the actin cytoskeleton highlights the differences in fibroblast adhesion between fabricated silicone surfaces. These unique figures illustrate that fibroblast adhesion and the reactions these cells have to silicone can be manipulated to enhance biointegration between the implant and the breast tissue. An alteration of fibroblast phenotype was also observed, exhibiting the propensity of these surfaces to induce categorical remodeling of fibroblasts. This unique study shows that fibroblast reactions to silicone topographies can be tailored to induce physiological changes in cells. This paves the way for further research necessary to develop more biocompatible constructs capable of eliminating capsular contracture by subverting the foreign body response.

Silk Film Topography Directs Collective Epithelial Cell Migration

PubMed Central

Rosenblatt, Mark I.

2012-01-01

The following study provides new insight into how surface topography dictates directed collective epithelial cell sheet growth through the guidance of individual cell movement. Collective cell behavior of migrating human corneal limbal-epithelial cell sheets were studied on highly biocompatible flat and micro-patterned silk film surfaces. The silk film edge topography guided the migratory direction of individual cells making up the collective epithelial sheet, which resulted in a 75% increase in total culture elongation. This was due to a 3-fold decrease in cell sheet migration rate efficiency for movement perpendicular to the topography edge. Individual cell migration direction is preferred in the parallel approach to the edge topography where localization of cytoskeletal proteins to the topography’s edge region is reduced, which results in the directed growth of the collective epithelial sheet. Findings indicate customized biomaterial surfaces may be created to direct both the migration rate and direction of tissue epithelialization. PMID:23185573

Pattern zoology in biaxially pre-stretched elastic bilayers: from wrinkles and creases to fracture-like ridges

NASA Astrophysics Data System (ADS)

Al-Rashed, Rashed; Lopez JiméNez, Francisco; Reis, Pedro

The wrinkling of elastic bilayers under compression has been explored as a method to produce reversible surface topography, with applications ranging from microfluidics to tunable optics. We introduce a new experimental system to study the effects of pre-stretching on the instability patterns that result from the biaxial compression of thin shells bound to an elastic substrate. A pre-stretched substrate is first prepared by pressurizing an initially flat elastomeric disk and bulging it into a nearly hemispherical thick shell. The substrate is then coated with a thin layer of a polymer suspension, which, upon curing, results in a thin shell of nearly constant thickness. Releasing the pre-stretch in the substrate by deflating the system places the outer film in a state of biaxial compression, resulting in a variety of buckling patterns. We explore the parameter space by systematically varying the pre-stretch, the substrate/film stiffness mismatch, and the thickness of the film. This results in a continuous transition between different buckling patterns, from the dimples and wrinkles that are traditionally associated with the buckling of elastic bilayers, to creases and high aspect ratio `fracture-like' ridges, where the pre-stretch plays an essential role.

Influence of nanophase titania topography on bacterial attachment and metabolism

PubMed Central

Park, Margaret R; Banks, Michelle K; Applegate, Bruce; Webster, Thomas J

2008-01-01

Surfaces with nanophase compared to conventional (or nanometer smooth) topographies are known to have different properties of area, charge, and reactivity. Previously published research indicates that the attachment of certain bacteria (such as Pseudomonas fluorescens 5RL) is higher on surfaces with nanophase compared to conventional topographies, however, their effect on bacterial metabolism is unclear. Results presented here show that the adhesion of Pseudomonas fluorescens 5RL and Pseudomonas putida TVA8 was higher on nanophase than conventional titania. Importantly, in terms of metabolism, bacteria attached to the nanophase surfaces had higher bioluminescence rates than on the conventional surfaces under all nutrient conditions. Thus, the results from this study show greater select bacterial metabolism on nanometer than conventional topographies, critical results with strong consequences for the design of improved biosensors for bacteria detection. PMID:19337418

Role of the unfolded protein response in topography-induced osteogenic differentiation in rat bone marrow mesenchymal stem cells.

PubMed

Shi, Mengqi; Song, Wen; Han, Tianxiao; Chang, Bei; Li, Guangwen; Jin, Jianfeng; Zhang, Yumei

2017-05-01

The topography of biomaterials can significantly influence the osteogenic differentiation of cells. Understanding topographical signal transduction is critical for developing biofunctional surfaces, but the current knowledge is insufficient. Recently, numerous reports have suggested that the unfolded protein response (UPR) and osteogenic differentiation are inter-linked. Therefore, we hypothesize that the UPR pathway may be involved in the topography-induced osteogenesis. In the present study, different surface topographies were fabricated on pure titanium foils and the endoplasmic reticulum (ER) stress and UPR pathway were systematically investigated. We found that ER stress and the PERK-eIF2α-ATF4 pathway were activated in a time- and topography-dependent manner. Additionally, the activation of the PERK-eIF2α-ATF4 pathway by different topographies was in line with their osteogenic induction capability. More specifically, the osteogenic differentiation could be enhanced or weakened when the PERK-eIF2α-ATF4 pathway was promoted or inhibited, respectively. Furthermore, tuning of the degree of ER stress with different concentrations of thapsigargin revealed that mild ER stress promotes osteogenic differentiation, whereas excessive ER stress inhibits osteogenic differentiation and causes apoptosis. Taken together, our findings suggest that the UPR may play a critical role in topography-induced osteogenic differentiation, which may help to provide new insights into topographical signal transduction. Suitable implant surface topography can effectively improve bioactivity and eventual bone affinity. However, the mechanism of topographical signaling transduction is unclear and criteria for designation of an appropriate implant surface topography is lacking. This study shows that the ER stress and PERK-eIF2α-ATF4 pathway were activated by micro- and micro/nano-topographies, which is corresponding to the osteogenic induction abilities of these topographies. Furthermore, we have found that mild ER stress improves osteogenic differentiation, whereas excessive ER stress inhibits osteogenic differentiation and causes apoptosis. Our findings demonstrate that the UPR plays a critical role in the topography induced osteogenic differentiation, which may help to provide new insights into the topographical signaling transduction. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Topography compensation for haptization of a mesh object and its stiffness distribution.

PubMed

Yim, Sunghoon; Jeon, Seokhee; Choi, Seungmoon

2015-01-01

This work was motivated by the need for perceptualizing nano-scale scientific data, e.g., those acquired by a scanning probe microscope, where collocated topography and stiffness distribution of a surface can be measured. Previous research showed that when the topography of a surface with spatially varying stiffness is rendered using the conventional penalty-based haptic rendering method, the topography perceived by the user could be significantly distorted from its original model. In the worst case, a higher region with a smaller stiffness value can be perceived to be lower than a lower region with a larger stiffness value. This problem was explained by the theory of force constancy: the user tends to maintain an invariant contact force when s/he strokes the surface to perceive its topography. In this paper, we present a haptization algorithm that can render the shape of a mesh surface and its stiffness distribution with high perceptual accuracy. Our algorithm adaptively changes the surface topography on the basis of the force constancy theory to deliver adequate shape information to the user while preserving the stiffness perception. We also evaluated the performance of the proposed haptization algorithm in comparison to the constraint-based algorithm by examining relevant proximal stimuli and carrying out a user experiment. Results demonstrated that our algorithm could improve the perceptual accuracy of shape and reduce the exploration time, thereby leading to more accurate and efficient haptization.

In Situ Scanning Tunneling Microscopy Topography Changes of Gold (111) in Aqueous Sulfuric Acid Produced by Electrochemical Surface Oxidation and Reduction and Relaxation Phenomena

NASA Astrophysics Data System (ADS)

Pasquale, M. A.; Nieto, F. J. Rodríguez; Arvia, A. J.

The electrochemical formation and reduction of O-layers on gold (111) films in 1 m sulfuric acid under different potentiodynamic routines are investigated utilizing in situ scanning tunneling microscopy. The surface dynamics is interpreted considering the anodic and cathodic reaction pathways recently proposed complemented with concurrent relaxation phenomena occurring after gold (111) lattice mild disruption (one gold atom deep) and moderate disruption (several atoms deep). The dynamics of both oxidized and reduced gold topographies depends on the potentiodynamic routine utilized to form OH/O surface species. The topography resulting from a mild oxidative disruption is dominated by quasi-2D holes and hillocks of the order of 5 nm, involving about 500-600 gold atoms each, and their coalescence. A cooperative turnover process at the O-layer, in which the anion ad-layer and interfacial water play a key role, determines the oxidized surface topography. The reduction of these O-layers results in gold clusters, their features depending on the applied potential routine. A moderate oxidative disruption produces a surface topography of hillocks and holes several gold atoms high and deep, respectively. The subsequent reduction leads to a spinodal gold pattern. Concurrent coalescence appears to be the result of an Ostwald ripening that involves the surface diffusion of both gold atoms and clusters. These processes produce an increase in surface roughness and an incipient gold faceting. The dynamics of different topographies can be qualitatively explained employing the arguments from colloidal science theory. For 1.1 V ≤ E ≅ Epzc weak electrostatic repulsions favor gold atom/cluster coalescence, whereas for E < Epzc the attenuated electrostatic repulsions among gold surfaces stabilize small clusters over the substrate producing string-like patterns.

Synergistic responses of superficial chemistry and micro topography of titanium created by wire-type electric discharge machining.

PubMed

Kataoka, Yu; Tamaki, Yukimichi; Miyazaki, Takashi

2011-01-01

Wire-type electric discharge machining has been applied to the manufacture of endosseous titanium implants as this computer associated technique allows extremely accurate complex sample shaping with an optimal micro textured surface during the processing. Since the titanium oxide layer is sensitively altered by each processing, the authors hypothesized that this technique also up-regulates biological responses through the synergistic effects of the superficial chemistry and micro topography. To evaluate the respective in vitro cellular responses on the superficial chemistry and micro topography of titanium surface processed by wire-type electric discharge, we used titanium-coated epoxy resin replica of the surface. An oxide layer on the titanium surface processed by wire-type electric discharge activated the initial responses of osteoblastic cells through an integrin-mediated mechanism. Since the mRNA expression of ALP on those replicas was up-regulated compared to smooth titanium samples, the micro topography of a titanium surface processed by wire-type electric discharge promotes the osteogenic potential of cells. The synergistic response of the superficial chemistry and micro topography of titanium processed by wire-type electric discharge was demonstrated in this study.

Effect of surface topography and bioactive properties on early adhesion and growth behavior of mouse preosteoblast MC3T3-E1 cells.

PubMed

Li, Na; Chen, Gang; Liu, Jue; Xia, Yang; Chen, Hanbang; Tang, Hui; Zhang, Feimin; Gu, Ning

2014-10-08

The effects of bioactive properties and surface topography of biomaterials on the adhesion and spreading properties of mouse preosteoblast MC3T3-E1 cells was investigated by preparation of different surfaces. Poly lactic-co-glycolic acid (PLGA) electrospun fibers (ES) were produced as a porous rough surface. In our study, coverslips were used as a substrate for the immobilization of 3,4-dihydroxyphenylalanine (DOPA) and collagen type I (COL I) in the preparation of bioactive surfaces. In addition, COL I was immobilized onto porous electrospun fibers surfaces (E-COL) to investigate the combined effects of bioactive molecules and topography. Untreated coverslips were used as controls. Early adhesion and growth behavior of MC3T3-E1 cells cultured on the different surfaces were studied at 6, 12, and 24 h. Evaluation of cell adhesion and morphological changes showed that the all the surfaces were favorable for promoting the adhesion and spreading of cells. CCK-8 assays and flow cytometry revealed that both topography and bioactive properties were favorable for cell growth. Analysis of β1, α1, α2, α5, α10 and α11 integrin expression levels by immunofluorescence, real-time RT-PCR, and Western blot and indicated that surface topography plays an important role in the early stage of cell adhesion. However, the influence of topography and bioactive properties of surfaces on integrins is variable. Compared with any of the topographic or bioactive properties in isolation, the combined effect of both types of properties provided an advantage for the growth and spreading of MC3T3-E1 cells. This study provides a new insight into the functions and effects of topographic and bioactive modifications of surfaces at the interface between cells and biomaterials for tissue engineering.

Localization of burn mark under an abnormal topography on MOSFET chip surface using liquid crystal and emission microscopy tools.

PubMed

Lau, C K; Sim, K S; Tso, C P

2011-01-01

This article focuses on the localization of burn mark in MOSFET and the scanning electron microscope (SEM) inspection on the defect location. When a suspect abnormal topography is shown on the die surface, further methods to pin-point the defect location is necessary. Fault localization analysis becomes important because an abnormal spot on the chip surface may and may not have a defect underneath it. The chip surface topography can change due to the catastrophic damage occurred at layers under the chip surface, but it could also be due to inconsistency during metal deposition in the wafer fabrication process. Two localization techniques, liquid crystal thermography and emission microscopy, were performed to confirm that the abnormal topography spot is the actual defect location. The tiny burn mark was surfaced by performing a surface decoration at the defect location using hot hydrochloric acid. SEM imaging, which has the high magnification and three-dimensional capabilities, was used to capture the images of the burn mark. Copyright © 2011 Wiley Periodicals, Inc.

Quantitative characterization of surface topography using spectral analysis

NASA Astrophysics Data System (ADS)

Jacobs, Tevis D. B.; Junge, Till; Pastewka, Lars

2017-03-01

Roughness determines many functional properties of surfaces, such as adhesion, friction, and (thermal and electrical) contact conductance. Recent analytical models and simulations enable quantitative prediction of these properties from knowledge of the power spectral density (PSD) of the surface topography. The utility of the PSD is that it contains statistical information that is unbiased by the particular scan size and pixel resolution chosen by the researcher. In this article, we first review the mathematical definition of the PSD, including the one- and two-dimensional cases, and common variations of each. We then discuss strategies for reconstructing an accurate PSD of a surface using topography measurements at different size scales. Finally, we discuss detecting and mitigating artifacts at the smallest scales, and computing upper/lower bounds on functional properties obtained from models. We accompany our discussion with virtual measurements on computer-generated surfaces. This discussion summarizes how to analyze topography measurements to reconstruct a reliable PSD. Analytical models demonstrate the potential for tuning functional properties by rationally tailoring surface topography—however, this potential can only be achieved through the accurate, quantitative reconstruction of the PSDs of real-world surfaces.

Surface topography due to convection in a variable viscosity fluid - Application to short wavelength gravity anomalies in the central Pacific Ocean

NASA Technical Reports Server (NTRS)

Lin, J.; Parmentier, E. M.

1985-01-01

Finite difference calculations of thermal convection in a fluid layer with a viscosity exponentially decreasing with temperature are performed in the context of examining the topography and gravity anomalies due to mantle convection. The surface topography and gravity anomalies are shown to be positive over regions of ascending flow and negative over regions of descending flow; at large Rayleigh numbers the amplitude of surface topography is inferred to depend on Rayleigh number to the power of 7/9. Compositional stratifications of the mantle is proposed as a mechanism for confining small-scale convection to a thin layer. A comparative analysis of the results with other available models is included.

Human Fetal Osteoblast Response on Poly(Methyl Methacrylate)/Polystyrene Demixed Thin Film Blends: Surface Chemistry Vs Topography Effects.

PubMed

D'Sa, Raechelle A; Raj, Jog; Dickinson, Peter J; McCabe, Fiona; Meenan, Brian J

2016-06-22

Recent advances in materials sciences have allowed for the development and fabrication of biomaterials that are capable of providing requisite cues to instigate cells to respond in a predictable fashion. We have developed a series of poly(methyl methacrylate)/polystyrene (PMMA/PS) polymer demixed thin films with nanotopographies ranging from nanoislands to nanopits to study the response of human fetal osteoblast cells (hFOBs). When PMMA was in excess in the blend composition, a nanoisland topography dominated, whereas a nanopit topography dominated when PS was in excess. PMMA was found to segregate to the top of the nanoisland morphology with PS preferring the substrate interface. To further ascertain the effects of surface chemistry vs topography, we plasma treated the polymer demixed films using an atmospheric pressure dielectric barrier discharge reactor to alter the surface chemistry. Our results have shown that hFOBs did not have an increased short-term cellular response on pristine polymer demixed surfaces. However, increasing the hydrophilicty/wettability of the surfaces by oxygen functionalization causes an increase in the cellular response. These results indicate that topography alone is not sufficient to induce a positive cellular response, but the underlying surface chemistry is also important in regulating cell function.

Topography of Vesta Surface

NASA Image and Video Library

2011-08-26

This view of the topography of asteroid Vesta surface is composed of several images obtained with the framing camera on NASA Dawn spacecraft on August 6, 2011. The image mosaic is shown superimposed on a digital terrain model.

Quantitative surface topography assessment of directly compressed and roller compacted tablet cores using photometric stereo image analysis.

PubMed

Allesø, Morten; Holm, Per; Carstensen, Jens Michael; Holm, René

2016-05-25

Surface topography, in the context of surface smoothness/roughness, was investigated by the use of an image analysis technique, MultiRay™, related to photometric stereo, on different tablet batches manufactured either by direct compression or roller compaction. In the present study, oblique illumination of the tablet (darkfield) was considered and the area of cracks and pores in the surface was used as a measure of tablet surface topography; the higher a value, the rougher the surface. The investigations demonstrated a high precision of the proposed technique, which was able to rapidly (within milliseconds) and quantitatively measure the obtained surface topography of the produced tablets. Compaction history, in the form of applied roll force and tablet punch pressure, was also reflected in the measured smoothness of the tablet surfaces. Generally it was found that a higher degree of plastic deformation of the microcrystalline cellulose resulted in a smoother tablet surface. This altogether demonstrated that the technique provides the pharmaceutical developer with a reliable, quantitative response parameter for visual appearance of solid dosage forms, which may be used for process and ultimately product optimization. Copyright © 2015 Elsevier B.V. All rights reserved.

Characterizing Arctic sea ice topography and atmospheric form drag using high-resolution IceBridge data

NASA Astrophysics Data System (ADS)

Petty, A.; Tsamados, M.; Kurtz, N. T.; Farrell, S. L.; Newman, T.; Harbeck, J.; Feltham, D. L.; Richter-Menge, J.

2015-12-01

Here we present a detailed analysis of Arctic sea ice topography using high resolution, three-dimensional surface elevation data from the NASA Operation IceBridge Airborne Topographic Mapper (ATM) laser altimeter. We derive novel ice topography statistics from 2009-2014 across both first-year and multiyear ice regimes - including the height, area coverage, orientation and spacing of distinct surface features. The sea ice topography exhibits strong spatial variability, including increased surface feature (e.g. pressure ridge) height and area coverage within the multi-year ice regions. The ice topography also shows a strong coastal dependency, with the feature height and area coverage increasing as a function of proximity to the nearest coastline, especially north of Greenland and the Canadian Archipelago. The ice topography data have also been used to explicitly calculate atmospheric drag coefficients over Arctic sea ice; utilizing existing relationships regarding ridge geometry and their impact on form drag. The results are being used to calibrate the recent drag parameterization scheme included in the sea ice model CICE.

Airborne Lidar Simulator for the Lidar Surface Topography (LIST) Mission

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Krainak, Michael A.; Abshire, James B.; Cavanaugh, John; Valett, Susan; Ramos-Izquierdo, Luis

2010-01-01

In 2007, the National Research Council (NRC) completed its first decadal survey for Earth science at the request of NASA, NOAA, and USGS. The Lidar Surface Topography (LIST) mission is one of fifteen missions recommended by NRC, whose primary objectives are to map global topography and vegetation structure at 5 m spatial resolution, and to acquire global surface height mapping within a few years. NASA Goddard conducted an initial mission concept study for the LIST mission in 2007, and developed the initial measurement requirements for the mission.

On the ratio of dynamic topography and gravity anomalies in a dynamic Earth

NASA Astrophysics Data System (ADS)

Colli, L.; Ghelichkhan, S.; Bunge, H. P.

2016-12-01

Growing evidence from a variety of geologic indicators points to significant topography maintained convectively by viscous stresses in the mantle. However, while gravity is sensitive to dynamically supported topography, there are only small free-air gravity anomalies (<30 mGal) associated with Earth's long-wavelength topography. This has been used to suggest that surface heights computed assuming a complete isostatic equilibrium provide a good approximation to observed topography. Here we show that the apparent paradox is resolved by the well-established formalism of global, self-gravitating, viscously stratified Earth models. The models predict a complex relation between dynamic topography, mass, and gravity anomalies that is not summarized by a constant admittance—i.e., ratio of gravity anomalies to surface deflections—as one would infer from analytic flow solutions formulated in a half-space.

Asymmetric three-dimensional topography over mantle plumes.

PubMed

Burov, Evgueni; Gerya, Taras

2014-09-04

The role of mantle-lithosphere interactions in shaping surface topography has long been debated. In general, it is supposed that mantle plumes and vertical mantle flows result in axisymmetric, long-wavelength topography, which strongly differs from the generally asymmetric short-wavelength topography created by intraplate tectonic forces. However, identification of mantle-induced topography is difficult, especially in the continents. It can be argued therefore that complex brittle-ductile rheology and stratification of the continental lithosphere result in short-wavelength modulation and localization of deformation induced by mantle flow. This deformation should also be affected by far-field stresses and, hence, interplay with the 'tectonic' topography (for example, in the 'active/passive' rifting scenario). Testing these ideas requires fully coupled three-dimensional numerical modelling of mantle-lithosphere interactions, which so far has not been possible owing to the conceptual and technical limitations of earlier approaches. Here we present new, ultra-high-resolution, three-dimensional numerical experiments on topography over mantle plumes, incorporating a weakly pre-stressed (ultra-slow spreading), rheologically realistic lithosphere. The results show complex surface evolution, which is very different from the smooth, radially symmetric patterns usually assumed as the canonical surface signature of mantle upwellings. In particular, the topography exhibits strongly asymmetric, small-scale, three-dimensional features, which include narrow and wide rifts, flexural flank uplifts and fault structures. This suggests a dominant role for continental rheological structure and intra-plate stresses in controlling dynamic topography, mantle-lithosphere interactions, and continental break-up processes above mantle plumes.

Assessing Impact Direction in 3-point Bending of Human Femora: Incomplete Butterfly Fractures and Fracture Surfaces,.

PubMed

Isa, Mariyam I; Fenton, Todd W; Deland, Trevor; Haut, Roger C

2018-01-01

Current literature associates bending failure with butterfly fracture, in which fracture initiates transversely at the tensile surface of a bent bone and branches as it propagates toward the impact surface. The orientation of the resulting wedge fragment is often considered diagnostic of impact direction. However, experimental studies indicate bending does not always produce complete butterfly fractures or produces wedge fragments variably in tension or compression, precluding their use in interpreting directionality. This study reports results of experimental 3-point bending tests on thirteen unembalmed human femora. Complete fracture patterns varied following bending failure, but incomplete fractures and fracture surface characteristics were observed in all impacted specimens. A flat, billowy fracture surface was observed in tension, while jagged, angular peaks were observed in compression. Impact direction was accurately reconstructed using incomplete tension wedge butterfly fractures and tension and compression fracture surface criteria in all thirteen specimens. © 2017 American Academy of Forensic Sciences.

X-ray fractography on fatigue fractured surface of austenitic stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yajima, Zenjiro; Tokuyama, Hideki; Kibayashi, Yasuo

1995-12-31

X-ray diffraction observation of the material internal structure beneath fracture surfaces provide fracture analysis with useful information to investigate the conditions and mechanisms of fracture. X-ray fractography is a generic name given to this technique. In the present study, X-ray fractography was applied to fatigue fracture surfaces of austenitic stainless steel (AISI 304) which consisted of solution treatment. The fatigue tests were carried out on compact tension (CT) specimens. The plastic strain on the fracture surface was estimated from measuring the line broadening of X-ray diffraction profiles. The line broadening of X-ray diffraction profiles was measured on and beneath fatiguemore » fracture surfaces. The depth of the plastic zone left on fracture surfaces was evaluated from the line broadening. The results are discussed on the basis of fracture mechanics.« less

Direct imaging of defect formation in strained organic flexible electronics by Scanning Kelvin Probe Microscopy

PubMed Central

Cramer, Tobias; Travaglini, Lorenzo; Lai, Stefano; Patruno, Luca; de Miranda, Stefano; Bonfiglio, Annalisa; Cosseddu, Piero; Fraboni, Beatrice

2016-01-01

The development of new materials and devices for flexible electronics depends crucially on the understanding of how strain affects electronic material properties at the nano-scale. Scanning Kelvin-Probe Microscopy (SKPM) is a unique technique for nanoelectronic investigations as it combines non-invasive measurement of surface topography and surface electrical potential. Here we show that SKPM in non-contact mode is feasible on deformed flexible samples and allows to identify strain induced electronic defects. As an example we apply the technique to investigate the strain response of organic thin film transistors containing TIPS-pentacene patterned on polymer foils. Controlled surface strain is induced in the semiconducting layer by bending the transistor substrate. The amount of local strain is quantified by a mathematical model describing the bending mechanics. We find that the step-wise reduction of device performance at critical bending radii is caused by the formation of nano-cracks in the microcrystal morphology of the TIPS-pentacene film. The cracks are easily identified due to the abrupt variation in SKPM surface potential caused by a local increase in resistance. Importantly, the strong surface adhesion of microcrystals to the elastic dielectric allows to maintain a conductive path also after fracture thus providing the opportunity to attenuate strain effects. PMID:27910889

Evapotranspiration and runoff from large land areas: Land surface hydrology for atmospheric general circulation models

NASA Technical Reports Server (NTRS)

Famiglietti, J. S.; Wood, Eric F.

1993-01-01

A land surface hydrology parameterization for use in atmospheric GCM's is presented. The parameterization incorporates subgrid scale variability in topography, soils, soil moisture and precipitation. The framework of the model is the statistical distribution of a topography-soils index, which controls the local water balance fluxes, and is therefore taken to represent the large land area. Spatially variable water balance fluxes are integrated with respect to the topography-soils index to yield our large topography-soils distribution, and interval responses are weighted by the probability of occurrence of the interval. Grid square averaged land surface fluxes result. The model functions independently as a macroscale water balance model. Runoff ratio and evapotranspiration efficiency parameterizations are derived and are shown to depend on the spatial variability of the above mentioned properties and processes, as well as the dynamics of land surface-atmosphere interactions.

Applications of corneal topography and tomography: a review.

PubMed

Fan, Rachel; Chan, Tommy Cy; Prakash, Gaurav; Jhanji, Vishal

2018-03-01

Corneal imaging is essential for diagnosing and management of a wide variety of ocular diseases. Corneal topography is used to characterize the shape of the cornea, specifically, the anterior surface of the cornea. Most corneal topographical systems are based on Placido disc that analyse rings that are reflected off the corneal surface. The posterior corneal surface cannot be characterized using Placido disc technology. Imaging of the posterior corneal surface is useful for diagnosis of corneal ectasia. Unlike corneal topographers, tomographers generate a three-dimensional recreation of the anterior segment and provide information about the corneal thickness. Scheimpflug imaging is one of the most commonly used techniques for corneal tomography. The cross-sectional images generated by a rotating Scheimpflug camera are used to locate the anterior and posterior corneal surfaces. The clinical uses of corneal topography include, diagnosis of corneal ectasia, assessment of corneal astigmatism, and refractive surgery planning. This review will discuss the applications of corneal topography and tomography in clinical practice. © 2017 Royal Australian and New Zealand College of Ophthalmologists.

Optical properties and surface topography of CdCl2 activated CdTe thin films

NASA Astrophysics Data System (ADS)

Patel, S. L.; Purohit, A.; Chander, S.; Dhaka, M. S.

2018-05-01

The effect of post-CdCl2 heat treatment on optical properties and surface topography of evaporated CdTe thin films is investigated. The pristine and thermally annealed films were subjected to UV-Vis spectrophotometer and atomic force microscopy (AFM) to investigate the optical properties and surface topography, respectively. The absorbance is found to be maximum (˜90%) at 320°C temperature and transmittance found to be minimum and almost constant in ultraviolet and visible regions. The direct band gap is increased from 1.42 eV to 2.12 eV with post-CdCl2 annealing temperature. The surface topography revealed that the uniformity is improved with annealing temperature and average surface roughness is found in the range of 83.3-144.3 nm as well as grains have cylindrical hill-like shapes. The investigated results indicate that the post-CdCl2 treated films annealed at 320°C may be well-suitable for thin film solar cells as an absorber layer.

Patterning of Novel Breast Implant Surfaces by Enhancing Silicone Biocompatibility, Using Biomimetic Topographies

PubMed Central

Barr, S.; Hill, E.; Bayat, A.

2010-01-01

Introduction and Aims: Silicone biocompatibility is dictated by cell-surface interaction and its understanding is important in the field of implantation. The role of surface topography and its associated cellular morphology needs investigation to identify qualities that enhance silicone surface biocompatability. This study aims to create well-defined silicone topographies and examine how breast tissue–derived fibroblasts react and align to these surfaces. Methods: Photolithographic microelectronic techniques were modified to produce naturally inspired topographies in silicone, which were cultured with breast tissue–derived human fibroblasts. Using light, immunofluorescent and atomic force microscopy, the cytoskeletal reaction of fibroblasts to these silicone surfaces was investigated. Results: Numerous, well-defined micron-sized pillars, pores, grooves, and ridges were manufactured and characterized in medical grade silicone. Inimitable immunofluorescent microscopy represented in our high magnification images of vinculin, vimentin, and the actin cytoskeleton highlights the differences in fibroblast adhesion between fabricated silicone surfaces. These unique figures illustrate that fibroblast adhesion and the reactions these cells have to silicone can be manipulated to enhance biointegration between the implant and the breast tissue. An alteration of fibroblast phenotype was also observed, exhibiting the propensity of these surfaces to induce categorical remodeling of fibroblasts. Conclusions: This unique study shows that fibroblast reactions to silicone topographies can be tailored to induce physiological changes in cells. This paves the way for further research necessary to develop more biocompatible constructs capable of eliminating capsular contracture by subverting the foreign body response. PMID:20458346

Biological Response of Human Bone Marrow-Derived Mesenchymal Stem Cells to Commercial Tantalum Coatings with Microscale and Nanoscale Surface Topographies

NASA Astrophysics Data System (ADS)

Skoog, Shelby A.; Kumar, Girish; Goering, Peter L.; Williams, Brian; Stiglich, Jack; Narayan, Roger J.

2016-06-01

Tantalum is a promising orthopaedic implant coating material due to its robust mechanical properties, corrosion resistance, and excellent biocompatibility. Previous studies have demonstrated improved biocompatibility and tissue integration of surface-treated tantalum coatings compared to untreated tantalum. Surface modification of tantalum coatings with biologically inspired microscale and nanoscale features may be used to evoke optimal tissue responses. The goal of this study was to evaluate commercial tantalum coatings with nanoscale, sub-microscale, and microscale surface topographies for orthopaedic and dental applications using human bone marrow-derived mesenchymal stem cells (hBMSCs). Tantalum coatings with different microscale and nanoscale surface topographies were fabricated using a diffusion process or chemical vapor deposition. Biological evaluation of the tantalum coatings using hBMSCs showed that tantalum coatings promote cellular adhesion and growth. Furthermore, hBMSC adhesion to the tantalum coatings was dependent on surface feature characteristics, with enhanced cell adhesion on sub-micrometer- and micrometer-sized surface topographies compared to hybrid nano-/microstructures. Nanostructured and microstructured tantalum coatings should be further evaluated to optimize the surface coating features to promote osteogenesis and enhance osseointegration of tantalum-based orthopaedic implants.

The Comprehensive AOCMF Classification System: Mandible Fractures-Level 3 Tutorial

PubMed Central

Cornelius, Carl-Peter; Audigé, Laurent; Kunz, Christoph; Rudderman, Randal; Buitrago-Téllez, Carlos H.; Frodel, John; Prein, Joachim

2014-01-01

This tutorial outlines the details of the AOCMF image-based classification system for fractures of the mandibular arch (i.e. the non-condylar mandible) at the precision level 3. It is the logical expansion of the fracture allocation to topographic mandibular sites outlined in level 2, and is based on three-dimensional (3D) imaging techniques/computed tomography (CT)/cone beam CT). Level 3 allows an anatomical description of the individual conditions of the mandibular arch such as the preinjury dental state and the degree of alveolar atrophy. Trauma sequelae are then addressed: (1) tooth injuries and periodontal trauma, (2) fracture involvement of the alveolar process, (3) the degree of fracture fragmentation in three categories (none, minor, and major), and (4) the presence of bone loss. The grading of fragmentation needs a 3D evaluation of the fracture area, allowing visualization of the outer and inner mandibular cortices. To document these fracture features beyond topography the alphanumeric codes are supplied with distinctive appendices. This level 3 tutorial is accompanied by a brief survey of the peculiarities of the edentulous atrophic mandible. Illustrations and a few case examples serve as instruction and reference to improve the understanding and application of the presented features. PMID:25489389

Using surface curvature to map geomorphic process regimes in a bedrock landscape, Henry Mountains, Utah

NASA Astrophysics Data System (ADS)

Corbett, S.; Sklar, L. S.; Davis, J.

2009-12-01

Linkages between form and process are much better understood in soil-mantled landscapes than in bedrock landscapes, despite the wide occurrence of bedrock landscapes in arid and mountainous terrain. Soil-mantled hillslope topography can be characterized by hillslope gradient and its spatial derivative, which is commonly referred to as curvature and defined as the Laplacian of elevation. Surface curvature can also be quantified using techniques that are invariant to the orientation of the surface. These approaches are useful in many geoscience applications, including structural analysis of folded surfaces within deforming crustal blocks. Here we explore the use of surface curvature of bedrock topography as a metric to identify and map distinct geomorphic process regimes in a landscape devoid of soil cover. Our study site is Simpson Creek, a 2.5 km2 watershed on the east flank of Mt. Hillers in the Henry Mountains, Utah, which drains to the Colorado River in Glen Canyon. The land surface is entirely exposed Navajo Sandstone bedrock, with isolated patches of wind-blown sand deposits. The channel network is discontinuous, with alternating reaches of steep, deeply-incised, frequently-potholed slots, and lower-gradient, sand-bedded channels. Hillslope topography is characterized by dome-shaped and sub-linear ridges, and is influenced by prominent structural joints. We calculate two measures of the surface-normal curvature using an ALSM-derived digital elevation model. The mean and Gaussian surface curvatures are the average and product respectively of the magnitudes of the maximum and minimum curvature vectors, obtained by differentiating a polynomial fit at each point in a grid with 1 m spacing. Plots of mean versus Gaussian curvature reveal distinct clusters of landscape elements, which we associate with specific process regimes. In this parameter space, there are four quadrants, classified as dome, basin, synformal saddle and antiformal saddle. The channel and valley network corresponds to negative mean curvature, where concave and convex profile segments plot as basins and synformal saddles (positive and negative Gaussian curvature) respectively. We are able to use surface curvature to map what can be interpreted as bedrock channel width, as well as knickpoints, sand-bedrock bed transitions, and even individual large potholes. The tips of the channel network also have a distinct surface-curvature signature, and are associated with prominent polygonal bedrock fracturing at the sub-meter scale. In the hillslope portion of the landscape (positive mean curvature), the distribution of landscape elements has several modes, including a characteristic dome curvature that may be associated with sheet jointing and weathering-influenced exfoliation erosion, and an antiformal saddle curvature where solution pits occur, particularly on higher ridges most distant from the main-stem slot canyon channels. One key goal of this work is to quantify the effect of variable erosion rate on the distribution of process regime as expressed by these characteristic modes of bedrock surface curvature.

Quantitative study of Xanthosoma violaceum leaf surfaces using RIMAPS and variogram techniques.

PubMed

Favret, Eduardo A; Fuentes, Néstor O; Molina, Ana M

2006-08-01

Two new imaging techniques (rotated image with maximum averaged power spectrum (RIMAPS) and variogram) are presented for the study and description of leaf surfaces. Xanthosoma violaceum was analyzed to illustrate the characteristics of both techniques. Both techniques produce a quantitative description of leaf surface topography. RIMAPS combines digitized images rotation with Fourier transform, and it is used to detect patterns orientation and characteristics of surface topography. Variogram relates the mathematical variance of a surface with the area of the sample window observed. It gives the typical scale lengths of the surface patterns. RIMAPS detects the morphological variations of the surface topography pattern between fresh and dried (herbarium) samples of the leaf. The variogram method finds the characteristic dimensions of the leaf microstructure, i.e., cell length, papillae diameter, etc., showing that there are not significant differences between dry and fresh samples. The results obtained show the robustness of RIMAPS and variogram analyses to detect, distinguish, and characterize leaf surfaces, as well as give scale lengths. Both techniques are tools for the biologist to study variations of the leaf surface when different patterns are present. The use of RIMAPS and variogram opens a wide spectrum of possibilities by providing a systematic, quantitative description of the leaf surface topography.

Reconstruction of Laser-Induced Surface Topography from Electron Backscatter Diffraction Patterns.

PubMed

Callahan, Patrick G; Echlin, McLean P; Pollock, Tresa M; De Graef, Marc

2017-08-01

We demonstrate that the surface topography of a sample can be reconstructed from electron backscatter diffraction (EBSD) patterns collected with a commercial EBSD system. This technique combines the location of the maximum background intensity with a correction from Monte Carlo simulations to determine the local surface normals at each point in an EBSD scan. A surface height map is then reconstructed from the local surface normals. In this study, a Ni sample was machined with a femtosecond laser, which causes the formation of a laser-induced periodic surface structure (LIPSS). The topography of the LIPSS was analyzed using atomic force microscopy (AFM) and reconstructions from EBSD patterns collected at 5 and 20 kV. The LIPSS consisted of a combination of low frequency waviness due to curtaining and high frequency ridges. The morphology of the reconstructed low frequency waviness and high frequency ridges matched the AFM data. The reconstruction technique does not require any modification to existing EBSD systems and so can be particularly useful for measuring topography and its evolution during in situ experiments.

Effect of Hydrofluoric Acid Etching Time on Titanium Topography, Chemistry, Wettability, and Cell Adhesion

PubMed Central

Zahran, R.; Rosales Leal, J. I.; Rodríguez Valverde, M. A.; Cabrerizo Vílchez, M. A.

2016-01-01

Titanium implant surface etching has proven an effective method to enhance cell attachment. Despite the frequent use of hydrofluoric (HF) acid, many questions remain unresolved, including the optimal etching time and its effect on surface and biological properties. The objective of this study was to investigate the effect of HF acid etching time on Ti topography, surface chemistry, wettability, and cell adhesion. These data are useful to design improved acid treatment and obtain an improved cell response. The surface topography, chemistry, dynamic wetting, and cell adhesiveness of polished Ti surfaces were evaluated after treatment with HF acid solution for 0, 2; 3, 5, 7, or 10 min, revealing a time-dependent effect of HF acid on their topography, chemistry, and wetting. Roughness and wetting increased with longer etching time except at 10 min, when roughness increased but wetness decreased. Skewness became negative after etching and kurtosis tended to 3 with longer etching time. Highest cell adhesion was achieved after 5–7 min of etching time. Wetting and cell adhesion were reduced on the highly rough surfaces obtained after 10-min etching time. PMID:27824875

Influence of additive laser manufacturing parameters on surface using density of partially melted particles

NASA Astrophysics Data System (ADS)

Rosa, Benoit; Brient, Antoine; Samper, Serge; Hascoët, Jean-Yves

2016-12-01

Mastering the additive laser manufacturing surface is a real challenge and would allow functional surfaces to be obtained without finishing. Direct Metal Deposition (DMD) surfaces are composed by directional and chaotic textures that are directly linked to the process principles. The aim of this work is to obtain surface topographies by mastering the operating process parameters. Based on experimental investigation, the influence of operating parameters on the surface finish has been modeled. Topography parameters and multi-scale analysis have been used in order to characterize the DMD obtained surfaces. This study also proposes a methodology to characterize DMD chaotic texture through topography filtering and 3D image treatment. In parallel, a new parameter is proposed: density of particles (D p). Finally, this study proposes a regression modeling between process parameters and density of particles parameter.

Development of antifouling surfaces to reduce bacterial attachment

NASA Astrophysics Data System (ADS)

Graham, Mary Viola

Bacteria are exceptionally good at adhering to surfaces and forming complex structures known as biofilms. This process, known as biofouling, can cause problems for infrastructure (eg, clogging and damaging pipes), for the food industry (eg, contamination of processing surfaces and equipment, and for the medical industry (eg, contamination of indwelling medical devices). Accordingly, multiple strategies have been explored to combat biofouling, including chemical modification of surfaces, development of antibiotic coatings, and more recently, the use of engineered surface topography. When designed properly, engineered surface topographies can significantly reduce bacterial surface attachment, ultimately limiting surface colonization. In this work, we hypothesized that the morphology, size, spacing, and surface pre-treatment of topographical features should directly correlate with the size and shape of target organisms, in order to reduce biofouling. Topographical features with size and spacing from 0.25 to 2 mum were fabricated in silicone elastomer and tested against rod shaped bacteria with an average size of 0.5 x 2 mum and spherical bacteria (cocci) ranging from 0.5 - 1 μm in diameter. Antifouling properties of the different topographical features were tested in both static and flow-based assays, and under oxygen plasma-treated (hydrophilic) and untreated (hydrophobic) surface conditions. We found that surface pre-treatment universally affects the ability bacteria to attach to surfaces, while surface topography limits attachment in a manner dependent on the bacterial size/shape and the size/spacing of the topography.

Altitude and Configuration of the Potentiometric Surface in the Upper White Clay Creek and Lower West Branch Brandywine Creek Basins including Portions of Penn, London Grove, New Garden, Londonderry, West Marlborough, Highland, and East Fallowfield Townships and West Grove, Avondale, Modena, and South Coatesville boroughs, Chester County, Pennsylvania, May through July 2006

USGS Publications Warehouse

Hale, Lindsay B.

2007-01-01

INTRODUCTION Since 1984, the U.S. Geological Survey (USGS) has been mapping the altitude and configuration of the potentiometric surface in Chester County as part of an ongoing cooperative program to measure and describe the water resources of the county. These maps can be used to determine the general direction of ground-water flow and are frequently referenced by municipalities and developers to evaluate ground-water conditions for water supply and resource-protection requirements. For this study, the potentiometric surface was mapped for an area in south-central Chester County. The northern part of the map includes portions of Highland, East Fallowfield, Londonderry, and West Marlborough Townships and South Coatesville and Modena Boroughs. The southern part of the map includes portions of Londonderry, West Marlborough, Penn, London Grove, and New Garden Townships and West Grove and Avondale Boroughs. The study area is mostly underlain by metamorphic rocks of the Glenarm Supergroup including Peters Creek Schist, Octoraro Phyllite, Wissahickon Schist, Cockeysville Mrable, and Setters Quartzite; and by pegmatite, mafic gneiss, felsic gneiss, and diabase. Ground water is obtained from these bedrock formations by wells that intercept fractures. The altitude and configuration of the potentiometric surface was contoured from water levels measured on different dates in available wells during May through July 2006 and from the altitude of springs and perennial streams. Topography was used as a guide for contouring so that the altitude of the potentiometric surface was inferred nowhere to be higher than the land surface. The potentiometric surface shown on this map is an approximation of the water table. The altitude of the actual potentiometric surface may differ from the water table, especially in areas where wells are completed in a semi-confined zone or have long open intervals that reflect the composite hydraulic head of multiple water-yielding fractures. A composite head may differ from the potentiometric-surface altitude, particularly beneath hilltops and valleys where vertical hydraulic gradients are significant.

The effect of skin surface topography and skin colouration cues on perception of male facial age, health and attractiveness.

PubMed

Fink, B; Matts, P J; Brauckmann, C; Gundlach, S

2018-04-01

Previous studies investigating the effects of skin surface topography and colouration cues on the perception of female faces reported a differential weighting for the perception of skin topography and colour evenness, where topography was a stronger visual cue for the perception of age, whereas skin colour evenness was a stronger visual cue for the perception of health. We extend these findings in a study of the effect of skin surface topography and colour evenness cues on the perceptions of facial age, health and attractiveness in males. Facial images of six men (aged 40 to 70 years), selected for co-expression of lines/wrinkles and discolouration, were manipulated digitally to create eight stimuli, namely, separate removal of these two features (a) on the forehead, (b) in the periorbital area, (c) on the cheeks and (d) across the entire face. Omnibus (within-face) pairwise combinations, including the original (unmodified) face, were presented to a total of 240 male and female judges, who selected the face they considered younger, healthier and more attractive. Significant effects were detected for facial image choice, in response to skin feature manipulation. The combined removal of skin surface topography resulted in younger age perception compared with that seen with the removal of skin colouration cues, whereas the opposite pattern was found for health preference. No difference was detected for the perception of attractiveness. These perceptual effects were seen particularly on the forehead and cheeks. Removing skin topography cues (but not discolouration) in the periorbital area resulted in higher preferences for all three attributes. Skin surface topography and colouration cues affect the perception of age, health and attractiveness in men's faces. The combined removal of these features on the forehead, cheeks and in the periorbital area results in the most positive assessments. © 2018 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Dynamic sea surface topography from GEOS-3 altimetry - Determination of some dominant parameters

NASA Technical Reports Server (NTRS)

Mather, R. S.; Lerch, F. J.; Rizos, C.; Masters, E. G.; Hirsch, B.

1979-01-01

The second, third and fourth degree zonal harmonics of the quasi-stationary dynamic sea surface topography can be recovered from the GEOS-3 altimetry despite the adverse levels of noise indicated by the crossover discrepancies generated from the best orbits available at the end of 1977 and the GEOS-3 altimetry. Techniques for modelling the global sea surface topography are discussed along with methods for signal recovery in the presence of significant levels of noise. The analysis also provides a means of defining the geocentricity of the system of reference used in preparing the GEOS-3 ephemeris.

The effects of topography on magma chamber deformation models: Application to Mt. Etna and radar interferometry

NASA Astrophysics Data System (ADS)

Williams, Charles A.; Wadge, Geoff

We have used a three-dimensional elastic finite element model to examine the effects of topography on the surface deformation predicted by models of magma chamber deflation. We used the topography of Mt. Etna to control the geometry of our model, and compared the finite element results to those predicted by an analytical solution for a pressurized sphere in an elastic half-space. Topography has a significant effect on the predicted surface deformation for both displacement profiles and synthetic interferograms. Not only are the predicted displacement magnitudes significantly different, but also the map-view patterns of displacement. It is possible to match the predicted displacement magnitudes fairly well by adjusting the elevation of a reference surface; however, the horizontal pattern of deformation is still significantly different. Thus, inversions based on constant-elevation reference surfaces may not properly estimate the horizontal position of a magma chamber. We have investigated an approach where the elevation of the reference surface varies for each computation point, corresponding to topography. For vertical displacements and tilts this method provides a good fit to the finite element results, and thus may form the basis for an inversion scheme. For radial displacements, a constant reference elevation provides a better fit to the numerical results.

Procedure for estimating fracture energy from fracture surface roughness

DOEpatents

Williford, Ralph E.

1989-01-01

The fracture energy of a material is determined by first measuring the length of a profile of a section through a fractured surface of the material taken on a plane perpendicular to the mean plane of that surface, then determining the fractal dimensionality of the surface. From this, the yield strength of the material, and the Young's Modulus of that material, the fracture energy is calculated.

Simulating the Formation of Lunar Floor-Fracture Craters Using Elastoviscoplastic Relaxation

NASA Technical Reports Server (NTRS)

Dombard, A. J.; Gillis, J. J.

1999-01-01

Lunar floor-fracture craters formed during the height of mare basalt emplacement. Due to a general temporal and spatial relation with the maria, these craters, numbering some 200, may be diagnostic of the thermal structure of the crust during this time. As the name suggests, these craters exhibit brittle failure, generally limited to the central floor region. That, and a shallower depth than fresh lunar craters, has led to two main theories as to their formation: laccolith emplacement under the crater and viscous relaxation. The implications of each model for the state of the Moon's crust during this time are quite different, so the viability of each model must be checked. Laccolith emplacement has been treated elsewhere. However, previous attempts to study the relaxation of the craters have assumed only a uniform, Newtonian viscous response of the near surface to the topographic driving forces, and simply postulated that the fractures resulted from tensile stresses associated with floor uplift. Here, we use a more sophisticated rheological model that includes not only non-Newtonian viscous behavior (i.e., the viscosity is stress-dependent), but also incorporates elastic behavior and a plastic component to the rheology to directly simulate the formation of the floor fractures. The results of our simulations show that while elastoviscoplastic relaxation is potentially viable for larger floor-fracture craters, it is not viable for craters with diameters < or = 60 km, the size of the majority of floor-fracture craters. We employ the finite element method, a numerical technique well suited for boundary-value problems, via the commercially available MARC software package. To test the viability of topographic relaxation, our goal is to prepare the simulations as to maximize the amount of relaxation. We take advantage of the natural axisymmetry of craters, simulating one radial plane. Initial shapes are based on data for fresh craters from Pike. To simplify implementation, a fourth order polynomial is used for the basin, while a third order inverse function is used for the rim. This form closely approximates the long-wavelength behavior of complex craters, while ignoring higher-frequency topography, save the rim. This approximation is appropriate because crater relaxation is strongly controlled by long-wavelength topography. Loading is accomplished assuming a uniform gravity field (1.62 m/s-square) and a uniform density of 2900 kg/cubic m. The initial stress state is set to be hydrostatic, with an additional pressure term to account for any overlying topography. This additional pressure term is tapered exponentially with depth. While the simulations quickly settle on a preferred stress state, and while the final solution is fairly insensitive to the choice of the e-folding depth of the taper, selecting an e-folding depth close to the diameter of the crater sets the initial stress state near the preferred state. We assume a diuranally averaged surface temperature of -20 C, and allow temperature to increase with depth at a rate of 50 K//km. Assuming a thermal conductivity of 2 W/in/K, this gradient translates to a heat flow of 100mW/square m, an extremely high value for the Moon. Temperature, of course, will not increase without bound. To maximize relaxation, we allow our temperature profile to increase linearly until it reaches the solidus (assumed to be 1200C) at a depth of 24.4 km, at which point it is kept constant. The presence of melt will drop the bulk viscosity; however, we have no rheological control for partial melts. Therefore, we make no attempt to simulate this situation. Elastoviscoplastic rheological model. In general, geologic materials can behave in three main ways: elastically, viscously (via solid-state creep), and brittly (plasticity is a continuum approach to simulate this phenomenon). We combine these three deformation mechanisms in an extended Maxwell solid, where the total strain can be broken down into a simple summation of the elastic, creep, and plastic strains. In relaxation phenomena in general, the system takes advantage of any means possible to eliminate deviatoric stresses by relaxing away the topography. Previous analyses have only modeled the viscous response. Comparatively, the elastic response in our model can augment the relaxation, to a point. This effect decreases as the elastic response becomes stiffer; indeed, in the limit of infinite elastic Young's modulus (and with no plasticity), the solution converges on the purely viscous solution. Igneous rocks common to the lunar near-surface have Young's modulii in the range of 10-100 GPa. To maximize relaxation, we use a Young's modulus of 10 GPa. (There is negligible sensitivity to the other elastic modulus, the Poisson's ratio; we use 0.25.) For the viscous response, we use a flow law for steady-state creep in thoroughly dried Columbia diabase, because the high plagioclase (about 70 vol%) and orthopyroxene (about 17 vol%) content is similar to the composition of the lunar highland crust as described by remote sensing and sample studies: noritic anorthosite. This flow law is highly non-Newtonian, i.e., the viscosity is highly stress dependent. That, and the variability with temperature, stands in strong contrast to previous examinations of lunar floor-fracture crater relaxation. To model discrete, brittle faulting, we assume "Byerlee's rule," a standard geodynamical technique. We implement this "rule" with an-angle of internal friction of about 40 deg, and a higher-than-normal cohesion of about 3.2 MPa (to approximate the breaking of unfractured rock). The actual behavior of geologic materials is more complex than in our rheological model, so the uncertainties in the plasticity do not represent the state-of-the-art error. Additional information is contained in the original.

Integrated approach to estimate the ocean's time variable dynamic topography including its covariance matrix

NASA Astrophysics Data System (ADS)

Müller, Silvia; Brockmann, Jan Martin; Schuh, Wolf-Dieter

2015-04-01

The ocean's dynamic topography as the difference between the sea surface and the geoid reflects many characteristics of the general ocean circulation. Consequently, it provides valuable information for evaluating or tuning ocean circulation models. The sea surface is directly observed by satellite radar altimetry while the geoid cannot be observed directly. The satellite-based gravity field determination requires different measurement principles (satellite-to-satellite tracking (e.g. GRACE), satellite-gravity-gradiometry (GOCE)). In addition, hydrographic measurements (salinity, temperature and pressure; near-surface velocities) provide information on the dynamic topography. The observation types have different representations and spatial as well as temporal resolutions. Therefore, the determination of the dynamic topography is not straightforward. Furthermore, the integration of the dynamic topography into ocean circulation models requires not only the dynamic topography itself but also its inverse covariance matrix on the ocean model grid. We developed a rigorous combination method in which the dynamic topography is parameterized in space as well as in time. The altimetric sea surface heights are expressed as a sum of geoid heights represented in terms of spherical harmonics and the dynamic topography parameterized by a finite element method which can be directly related to the particular ocean model grid. Besides the difficult task of combining altimetry data with a gravity field model, a major aspect is the consistent combination of satellite data and in-situ observations. The particular characteristics and the signal content of the different observations must be adequately considered requiring the introduction of auxiliary parameters. Within our model the individual observation groups are combined in terms of normal equations considering their full covariance information; i.e. a rigorous variance/covariance propagation from the original measurements to the final product is accomplished. In conclusion, the developed integrated approach allows for estimating the dynamic topography and its inverse covariance matrix on arbitrary grids in space and time. The inverse covariance matrix contains the appropriate weights for model-data misfits in least-squares ocean model inversions. The focus of this study is on the North Atlantic Ocean. We will present the conceptual design and dynamic topography estimates based on time variable data from seven satellite altimeter missions (Jason-1, Jason-2, Topex/Poseidon, Envisat, ERS-2, GFO, Cryosat2) in combination with the latest GOCE gravity field model and in-situ data from the Argo floats and near-surface drifting buoys.

Tectonic controls on large landslide complex: Williams Fork Mountains near Dillon, Colorado

USGS Publications Warehouse

Kellogg, K.S.

2001-01-01

An extensive (~ 25 km2) landslide complex covers a large area on the west side of the Williams Fork Mountains in central Colorado. The complex is deeply weathered and incised, and in most places geomorphic evidence of sliding (breakaways, hummocky topography, transverse ridges, and lobate distal zones) are no longer visible, indicating that the main mass of the slide has long been inactive. However, localized Holocene reactivation of the landslide deposits is common above the timberline (at about 3300 m) and locally at lower elevations. Clasts within the complex, as long as several tens of meters, are entirely of crystalline basement (Proterozoic gneiss and granitic rocks) from the hanging wall of the Laramide (Late Cretaceous to Early Tertiary), west-directed Williams Range thrust, which forms the western structural boundary of the Colorado Front Range. Late Cretaceous shale and sandstone compose most footwall rocks. The crystalline hanging-wall rocks are pervasively fractured or shattered, and alteration to clay minerals is locally well developed. Sackung structures (trenches or small-scale grabens and upslope-facing scarps) are common near the rounded crest of the range, suggesting gravitational spreading of the fractured rocks and oversteepening of the mountain flanks. Late Tertiary and Quaternary incision of the Blue River Valley, just west of the Williams Fork Mountains, contributed to the oversteepening. Major landslide movement is suspected during periods of deglaciation when abundant meltwater increased pore-water pressure in bedrock fractures. A fault-flexure model for the development of the widespread fracturing and weakening of the Proterozoic basement proposes that the surface of the Williams Range thrust contains a concave-downward flexure, the axis of which coincides approximately with the contact in the footwall between Proterozoic basement and mostly Cretaceous rocks. Movement of brittle, hanging-wall rocks through the flexure during Laramide deformation pervasively fractured the hanging-wall rocks. ?? 2001 Elsevier Science B.V. All rights reserved.

Topography of calcium phosphate ceramics regulates primary cilia length and TGF receptor recruitment associated with osteogenesis.

PubMed

Zhang, Jingwei; Dalbay, Melis T; Luo, Xiaoman; Vrij, Erik; Barbieri, Davide; Moroni, Lorenzo; de Bruijn, Joost D; van Blitterswijk, Clemens A; Chapple, J Paul; Knight, Martin M; Yuan, Huipin

2017-07-15

The surface topography of synthetic biomaterials is known to play a role in material-driven osteogenesis. Recent studies show that TGFβ signalling also initiates osteogenic differentiation. TGFβ signalling requires the recruitment of TGFβ receptors (TGFβR) to the primary cilia. In this study, we hypothesize that the surface topography of calcium phosphate ceramics regulates stem cell morphology, primary cilia structure and TGFβR recruitment to the cilium associated with osteogenic differentiation. We developed a 2D system using two types of tricalcium phosphate (TCP) ceramic discs with identical chemistry. One sample had a surface topography at micron-scale (TCP-B, with a bigger surface structure dimension) whilst the other had a surface topography at submicron scale (TCP-S, with a smaller surface structure dimension). In the absence of osteogenic differentiation factors, human bone marrow stromal cells (hBMSCs) were more spread on TCP-S than on TCP-B with alterations in actin organization and increased primary cilia prevalence and length. The cilia elongation on TCP-S was similar to that observed on glass in the presence of osteogenic media and was followed by recruitment of transforming growth factor-β RII (p-TGFβ RII) to the cilia axoneme. This was associated with enhanced osteogenic differentiation of hBMSCs on TCP-S, as shown by alkaline phosphatase activity and gene expression for key osteogenic markers in the absence of additional osteogenic growth factors. Similarly, in vivo after a 12-week intramuscular implantation in dogs, TCP-S induced bone formation while TCP-B did not. It is most likely that the surface topography of calcium phosphate ceramics regulates primary cilia length and ciliary recruitment of p-TGFβ RII associated with osteogenesis and bone formation. This bioengineering control of osteogenesis via primary cilia modulation may represent a new type of biomaterial-based ciliotherapy for orthopedic, dental and maxillofacial surgery applications. The surface topography of synthetic biomaterials plays important roles in material-driven osteogenesis. The data presented herein have shown that the surface topography of calcium phosphate ceramics regulates mesenchymal stromal cells (e.g., human bone marrow mesenchymal stromal cells, hBMSCs) with respect to morphology, primary cilia structure and TGFβR recruitment to the cilium associated with osteogenic differentiation in vitro. Together with bone formation in vivo, our results suggested a new type of biomaterial-based ciliotherapy for orthopedic, dental and maxillofacial surgery by the bioengineering control of osteogenesis via primary cilia modulation. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Payload topography camera of Chang'e-3

NASA Astrophysics Data System (ADS)

Yu, Guo-Bin; Liu, En-Hai; Zhao, Ru-Jin; Zhong, Jie; Zhou, Xiang-Dong; Zhou, Wu-Lin; Wang, Jin; Chen, Yuan-Pei; Hao, Yong-Jie

2015-11-01

Chang'e-3 was China's first soft-landing lunar probe that achieved a successful roving exploration on the Moon. A topography camera functioning as the lander's “eye” was one of the main scientific payloads installed on the lander. It was composed of a camera probe, an electronic component that performed image compression, and a cable assembly. Its exploration mission was to obtain optical images of the lunar topography in the landing zone for investigation and research. It also observed rover movement on the lunar surface and finished taking pictures of the lander and rover. After starting up successfully, the topography camera obtained static images and video of rover movement from different directions, 360° panoramic pictures of the lunar surface around the lander from multiple angles, and numerous pictures of the Earth. All images of the rover, lunar surface, and the Earth were clear, and those of the Chinese national flag were recorded in true color. This paper describes the exploration mission, system design, working principle, quality assessment of image compression, and color correction of the topography camera. Finally, test results from the lunar surface are provided to serve as a reference for scientific data processing and application.

Surface topography characterization of brass alloys: lead brass (CuZn39Pb3) and lead free brass (CuZn21Si3P)

NASA Astrophysics Data System (ADS)

Reddy, Vijeth V.; Vedantha Krishna, Amogh; Schultheiss, Fredrik; Rosén, B.-G.

2017-06-01

Manufactured surfaces usually consist of topographical features which include both those put forth by the manufacturing process, and micro-features caused by disturbances during this process. Surface characterization basically involves study of these features which influence the functionality of the surface. This article focuses on characterization of the surface topography of machined lead brass and lead free brass. The adverse effect of lead on human health and the environment has led the manufacturing sector to focus on sustainable manufacturing of lead free brass, as well as how to maintain control of the surface integrity when substituting the lead content in the brass with silicon. The investigation includes defined areal surface parameters measured on the turned samples of lead- and lead free brass using an optical coherence scanning interferometer, CSI. This paper deals with the study of surface topography of turned samples of lead- and lead free brass. It is important to study the topographical characteristics of the brass samples which are the intermediate link between the manufacturing process variables and the functional behaviour of the surface. To numerically evaluate the sample’s surface topography and to validate the measurements for a significant study, a general statistical methodology is implemented. The results indicate higher surface roughness in turned samples of lead brass compared to lead free brass.

Exploring Nested Reaction Fronts to Understand How Oxygen Cracks Rocks, Carbonic and Sulfuric Acids Dissolve Rocks, and Water Transports Rocks during Weathering

NASA Astrophysics Data System (ADS)

Brantley, S. L.; Gu, X.; Sullivan, P. L.; Kim, H.; Stinchcomb, G. E.; Lebedeva, M.; Balashov, V. N.

2016-12-01

To first order, weathering is the reaction of rocks with oxidants (oxygen, nitrate, etc.), acids (carbonic, sulfuric, and organic acids), and water. To explore weathering we have been studying the depth intervals in soils, saprolite, and weathering rock where mineral reactions are localized - "reaction fronts". We limit the study to ridges or catchments in climates where precipitation is greater than potential evapotranspiration. For example, in the Susquehanna Shale Hills Critical Zone Observatory, we observe reaction fronts that generally define very rough surfaces in 3D that mimic the land surface topography, although with lower relief. Overall, the fronts form nested curved surfaces. In Shale Hills, the deepest reaction fronts are oxidation of pyrite, and dissolution of carbonate. The carbonate is inferred to dissolve at least partly due to the sulfuric acid produced by the pyrite. In addition to pyrite, chlorite also starts to oxidize at the water table. We hypothesize that these dissolution and oxidation reactions open pores and cause microfracturing that open the rock to infiltration of advecting meteoric waters. At much shallower depths, illite is observed to dissolve. In Shale Hills, these reaction fronts - pyrite, carbonate, illite - separate over meters beneath the ridges. Such separated reaction fronts have also been observed in other fractured lithologies where oxidation is the deepest reaction and is associated with weathering-induced fractures. In contrast, in some massive mafic rocks, reaction fronts are almost co-located. By studying the geometry of reaction fronts, it may be possible to elucidate the relative importance of how oxygen cracks rocks; carbonic, organic, and sulfuric acids dissolve rocks; and water mobilizes rock materials during weathering.

Fracture surfaces of granular pastes.

PubMed

Mohamed Abdelhaye, Y O; Chaouche, M; Van Damme, H

2013-11-01

Granular pastes are dense dispersions of non-colloidal grains in a simple or a complex fluid. Typical examples are the coating, gluing or sealing mortars used in building applications. We study the cohesive rupture of thick mortar layers in a simple pulling test where the paste is initially confined between two flat surfaces. After hardening, the morphology of the fracture surfaces was investigated, using either the box counting method to analyze fracture profiles perpendicular to the mean fracture plane, or the slit-island method to analyze the islands obtained by cutting the fracture surfaces at different heights, parallel to the mean fracture plane. The fracture surfaces were shown to exhibit scaling properties over several decades. However, contrary to what has been observed in the brittle or ductile fracture of solid materials, the islands were shown to be mass fractals. This was related to the extensive plastic flow involved in the fracture process.

Production of hybrid macro/micro/nano surface structures on Ti6Al4V surfaces by picosecond laser surface texturing and their antifouling characteristics.

PubMed

Rajab, Fatema H; Liauw, Christopher M; Benson, Paul S; Li, Lin; Whitehead, Kathryn A

2017-12-01

The development of surfaces which reduce biofouling has attracted much interest in practical applications. Three picosecond laser generated surface topographies (Ti1, Ti2, Ti3) on titanium were produced, treated with fluoroalkylsilane (FAS), then characterised using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Raman Spectroscopy, Fourier Transform Infra-Red (FTIR) spectroscopy, contact angle measurements and white light interference microscopy. The surfaces had a range of different macro/micro/nano topographies. Ti2 had a unique, surface topography with large blunt conical peaks and was predominantly a rutile surface with closely packed, self-assembled FAS; this was the most hydrophobic sample (water contact angle 160°; ΔG iwi was -135.29mJm -2 ). Bacterial attachment, adhesion and retention to the surfaces demonstrated that all the laser generated surfaces retained less bacteria than the control surface. This also occurred following the adhesion and retention assays when the bacteria were either not rinsed from the surfaces or were retained in static conditions for one hour. This work demonstrated that picosecond laser generated surfaces may be used to produce antiadhesive surfaces that significantly reduced surface fouling. It was determined that a tri-modally dimensioned surface roughness, with a blunt conical macro-topography, combined with a close-packed fluoroalkyl monolayer was required for an optimised superhydrophobic surface. These surfaces were effective even following surface immersion and static conditions for one hour, and thus may have applications in a number of food or medical industries. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of modified titanium surfaces physical and chemical characteristics

NASA Astrophysics Data System (ADS)

Lukaszewska-Kuska, Magdalena; Leda, Bartosz; Gajdus, Przemyslaw; Hedzelek, Wieslaw

2017-11-01

Development of dental implantology is focused, among other things, on devising active surface of the implant, conditioning acceleration of the implant's integration with the bone. Increased roughness, characteristic for group of implants with developed surface, altered topography and chemically modified implant's surface determines increased implants stability. In this study four different titanium surfaces modifications: turned (TS); aluminium oxide-blasted (Al2O3); resorbable material blasted (RBM); sandblast and then etched with a mixture of acids (SAE), were evaluated in terms of surfaces topography and chemical composition prior to in vivo analysis. Topography analysis revealed two groups: one with smooth, anisotropic, undeveloped TS surface and the second group with remaining surfaces presenting rough, isotropic, developed surfaces with added during blasting procedure aluminium for Al2O3 and calcium and phosphorus for RBM. Physical and chemical modifications of titanium surface change its microstructure (typical for SAE) and increase its roughness (highest for Al2O3-blasted and RBM surfaces). The introduced modifications develop titanium surface - 10 times for SAE surfaces, 16 times for Al2O3-blasted surfaces, and 20 times for RBM surfaces.

Simulating Fragmentation and Fluid-Induced Fracture in Disordered Media Using Random Finite-Element Meshes

DOE PAGES

Bishop, Joseph E.; Martinez, Mario J.; Newell, Pania

2016-11-08

Fracture and fragmentation are extremely nonlinear multiscale processes in which microscale damage mechanisms emerge at the macroscale as new fracture surfaces. Numerous numerical methods have been developed for simulating fracture initiation, propagation, and coalescence. In this paper, we present a computational approach for modeling pervasive fracture in quasi-brittle materials based on random close-packed Voronoi tessellations. Each Voronoi cell is formulated as a polyhedral finite element containing an arbitrary number of vertices and faces. Fracture surfaces are allowed to nucleate only at the intercell faces. Cohesive softening tractions are applied to new fracture surfaces in order to model the energy dissipatedmore » during fracture growth. The randomly seeded Voronoi cells provide a regularized discrete random network for representing fracture surfaces. The potential crack paths within the random network are viewed as instances of realizable crack paths within the continuum material. Mesh convergence of fracture simulations is viewed in a weak, or distributional, sense. The explicit facet representation of fractures within this approach is advantageous for modeling contact on new fracture surfaces and fluid flow within the evolving fracture network. Finally, applications of interest include fracture and fragmentation in quasi-brittle materials and geomechanical applications such as hydraulic fracturing, engineered geothermal systems, compressed-air energy storage, and carbon sequestration.« less

Simulating Fragmentation and Fluid-Induced Fracture in Disordered Media Using Random Finite-Element Meshes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bishop, Joseph E.; Martinez, Mario J.; Newell, Pania

Fracture and fragmentation are extremely nonlinear multiscale processes in which microscale damage mechanisms emerge at the macroscale as new fracture surfaces. Numerous numerical methods have been developed for simulating fracture initiation, propagation, and coalescence. In this paper, we present a computational approach for modeling pervasive fracture in quasi-brittle materials based on random close-packed Voronoi tessellations. Each Voronoi cell is formulated as a polyhedral finite element containing an arbitrary number of vertices and faces. Fracture surfaces are allowed to nucleate only at the intercell faces. Cohesive softening tractions are applied to new fracture surfaces in order to model the energy dissipatedmore » during fracture growth. The randomly seeded Voronoi cells provide a regularized discrete random network for representing fracture surfaces. The potential crack paths within the random network are viewed as instances of realizable crack paths within the continuum material. Mesh convergence of fracture simulations is viewed in a weak, or distributional, sense. The explicit facet representation of fractures within this approach is advantageous for modeling contact on new fracture surfaces and fluid flow within the evolving fracture network. Finally, applications of interest include fracture and fragmentation in quasi-brittle materials and geomechanical applications such as hydraulic fracturing, engineered geothermal systems, compressed-air energy storage, and carbon sequestration.« less

Mechanisms of Cdc42-mediated rat MSC differentiation on micro/nano-textured topography.

PubMed

Li, Guangwen; Song, Yanyan; Shi, Mengqi; Du, Yuanhong; Wang, Wei; Zhang, Yumei

2017-02-01

Micro/nano-textured titanium surface topography promotes osteoblast differentiation and the Wnt/β-catenin signaling pathway. However, the response of rat bone mesenchymal stem cells (MSCs) to micro/nano-textured topography, and the underlying mechanisms of its effects, are not well understood. We hypothesized that cell division cycle 42 protein (Cdc42), a key member of the Rho GTPases family, may regulate rat MSCs morphology and osteogenic differentiation by micro/nano-textured topography, and that crosstalk between Cdc42 and Wnt/β-catenin is the underlying mechanism. To confirm the hypothesis, we first tested rat MSCs' morphology, cytoskeleton, and osteogenic differentiation on micro/nano-textured topography. We then examined the cells' Wnt pathway and Cdc42 signaling activity. The results show that micro/nano-textured topography enhances MSCs' osteogenic differentiation. In addition, the cells' morphology and cytoskeletal reorganization were dramatically different on smooth surfaces and micropitted/nanotubular topography. Ligands of the canonical Wnt pathway, as well as accumulation of β-catenin in the nucleus, were up-regulated by micro/nano-textured topography. Cdc42 protein expression was markedly increased under these conditions; conversely, Cdc42 silencing significantly depressed the enhancement of MSCs osteogenic differentiation by micro/nano-textured topography. Moreover, Cdc42si attenuated p-GSK3β activation and resulted in β-catenin cytoplasmic degradation on the micro/nano-textured topography. Our results indicate that Cdc42 is a key modulator of rat MSCs morphology and cytoskeletal reorganization, and that crosstalk between Cdc42 and Wnt/β-catenin signaling though GSK3β regulates MSCs osteogenic differentiation by implant topographical cues. Topographical modification at micro- and nanoscale is widely applied to enhance the tissue integration properties of biomaterials. However, the response of bone mesenchymal stem cells (MSCs) to the micro/nano-textured topography and the underlying mechanisms are not well understood. This study shows that the micropitted/nanotubular hierarchical topography produced by etching and anodic oxidation treatment drives fusiform cell morphology, cytoskeletal reorganization as well as better MSCs osteogenic differentiation. The cross-talk between Cdc42 pathway and Wnt/β-catenin pathway though GSK3β modulates the osteoinductive effect of the micro/nano-textured topography on MSCs. This finding sheds light on a novel mechanism involved in micro/nano-textured surface-mediated MSCs osteogenic differentiation and is a major step in the development of new surface modifications aiming to accelerate and enhance the process of osseointegration. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Design and implementation of optical system for Placido-disc topography

NASA Astrophysics Data System (ADS)

Sui, Chenghua; Wo, Shengjie; Cai, Pinggen; Gao, Nan; Xu, Danyang; Han, Yonghao; Du, Chunnian

2017-11-01

Corneal topography provides powerful support in the diagnosis and treatment of corneal disease by displaying the corneal surface topography in data or image format. To realize the precise detection of corneal surface topography, an optical system for the corneal topography that is based on a Placido disc is designed, which includes a ring distribution on a Placido disc, an imaging system and a collimating illumination system. First, a mathematical model that is based on the corneal topography working principles is established with MATLAB to determine the distribution of white-and-black rings on the Placido disc, in which the ellipsoid facial rings-target of the Placido disc is utilized. Second, the imaging lens structure is designed and optimized by Zemax software. Last, the collimating illumination lens structure is designed by paraxial ray trace equations. The quality of the corneal topography, which is based on our designed optical system, is evaluated. The high-contrast image of uniformly distributed white-and-black rings is observed through the CCD camera. Our optical system for the corneal topography has high precision, with a measuring region of the cornea with a diameter of approximately 10 mm. Therefore, the creation of this optical system offers guidance for designing and improving the optical system of Placido-disc topography.

Duplex stainless steel fracture surface analysis using X-ray fractography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajanna, K.; Pathiraj, B.; Kolster, B.H.

1997-02-01

The fatigue fracture surface of a duplex stainless steel was analyzed using x-ray fractography. A lower than average austenite content was observed at the fracture surface due to the transformation of austenite into deformation-induced martensite. The influence of fatigue cycling on the transformation was confined to a depth of about 30 {micro}m below the fracture surface. X-ray analyses of both the ferrite-martensite and the austenite phases indicated residual stresses ({sigma}{sub r}) increasing with depth from the fracture surface and reaching a maximum some tens of microns below the fracture surface. The lower {sigma}{sub r} observed at the fracture surface hasmore » been attributed to the stress relaxation effects caused by the new fracture surfaces created in the crack growth process. The observed decrease in full width at half maximum (FWHM) in the ferrite-martensite phase was presumed to be due to the dynamic recovery effect that was likely to occur within the material close to the crack tip as a consequence of fatigue cycling.« less

Simulation of foulant bioparticle topography based on Gaussian process and its implications for interface behavior research

NASA Astrophysics Data System (ADS)

Zhao, Leihong; Qu, Xiaolu; Lin, Hongjun; Yu, Genying; Liao, Bao-Qiang

2018-03-01

Simulation of randomly rough bioparticle surface is crucial to better understand and control interface behaviors and membrane fouling. Pursuing literature indicated a lack of effective method for simulating random rough bioparticle surface. In this study, a new method which combines Gaussian distribution, Fourier transform, spectrum method and coordinate transformation was proposed to simulate surface topography of foulant bioparticles in a membrane bioreactor (MBR). The natural surface of a foulant bioparticle was found to be irregular and randomly rough. The topography simulated by the new method was quite similar to that of real foulant bioparticles. Moreover, the simulated topography of foulant bioparticles was critically affected by parameters correlation length (l) and root mean square (σ). The new method proposed in this study shows notable superiority over the conventional methods for simulation of randomly rough foulant bioparticles. The ease, facility and fitness of the new method point towards potential applications in interface behaviors and membrane fouling research.

Mechanical behavior and fracture characteristics of off-axis fiber composites. 1: Experimental investigation. [at the Lewis Research Center

NASA Technical Reports Server (NTRS)

Sinclair, J. H.; Chamis, C. C.

1977-01-01

The mechanical behavior, fracture surfaces, and fracture modes of unidirectional high-modulus graphite-fiber/epoxy composites subjected to off-axis tensile loads were investigated experimentally. The investigation included the generation of stress-strain-to-fracture data and scanning electron microscope studies of the fractured surfaces. The results led to the identification of fracture modes and distinct fracture surface characteristics for off-axis tensile loading. The results also led to the formulation of critical for identifying and characterizing these fracture modes and their associated fracture surfaces. The results presented and discussed herein were used in the theoretical investigation and comparisons described in Part 2. These results should also provide a good foundation for identifying, characterizing, and quantifying fracture modes in both off-axis and angle-plied laminates.

Preliminary estimates of Gulf Stream characteristics from TOPEX data and a precise gravimetric geoid

NASA Technical Reports Server (NTRS)

Rapp, Richard H.; Smith, Dru A.

1994-01-01

TOPEX sea surface height data has been used, with a gravimetric geoid, to calculate sea surface topography across the Gulf Stream. This topography was initially computed for nine tracks on cycles 21 to 29. Due to inaccurate geoid undulations on one track, results for eight tracks are reported. The sea surface topography estimates were used to calculate parameters that describe Gulf Stream characteristics from two models of the Gulf Stream. One model was based on a Gaussian representation of the velocity while the other was a hyperbolic representation of velocity or the sea surface topography. The parameters of the Gaussian velocity model fit were a width parameter, a maximum velocity value, and the location of the maximum velocity. The parameters of the hyperbolic sea surface topography model were the width, the height jump, position, and sea surface topography at the center of the stream. Both models were used for the eight tracks and nine cycles studied. Comparisons were made between the width parameters, the maximum velocities, and the height jumps. Some of the parameter estimates were found to be highly (0.9) correlated when the hyperbolic sea surface topography fit was carried out, but such correlations were reduced for either the Gaussian velocity fits or the hyperbolic velocity model fit. A comparison of the parameters derived from 1-year TOPEX data showed good agreement with values derived by Kelly (1991) using 2.5 years of Geosat data near 38 deg N, 66 deg W longitude. Accuracy of the geoid undulations used in the calculations was of order of +/- 16 cm with the accuracy of a geoid undulation difference equal to +/- 15 cm over a 100-km line in areas with good terrestrial data coverage. This paper demonstrates that our knowledge or geoid undulations and undulation differences, in a portion of the Gulf Stream region, is sufficiently accurate to determine characteristics of the jet when used with TOPEX altimeter data. The method used here has not been shown to be more accurate than methods that average altimeter data to form a reference surface used in analysis to obtain the Gulf Stream characteristics. However, the results show the geoid approach may be used in areas where lack of current meandering reduces the accuracy of the average surface procedure.

Groundwater flow and its effect on salt dissolution in Gypsum Canyon watershed, Paradox Basin, southeast Utah, USA

NASA Astrophysics Data System (ADS)

Reitman, Nadine G.; Ge, Shemin; Mueller, Karl

2014-09-01

Groundwater flow is an important control on subsurface evaporite (salt) dissolution. Salt dissolution can drive faulting and associated subsidence on the land surface and increase salinity in groundwater. This study aims to understand the groundwater flow system of Gypsum Canyon watershed in the Paradox Basin, Utah, USA, and whether or not groundwater-driven dissolution affects surface deformation. The work characterizes the groundwater flow and solute transport systems of the watershed using a three-dimensional (3D) finite element flow and transport model, SUTRA. Spring samples were analyzed for stable isotopes of water and total dissolved solids. Spring water and hydraulic conductivity data provide constraints for model parameters. Model results indicate that regional groundwater flow is to the northwest towards the Colorado River, and shallow flow systems are influenced by topography. The low permeability obtained from laboratory tests is inconsistent with field observed discharges, supporting the notion that fracture permeability plays a significant role in controlling groundwater flow. Model output implies that groundwater-driven dissolution is small on average, and cannot account for volume changes in the evaporite deposits that could cause surface deformation, but it is speculated that dissolution may be highly localized and/or weaken evaporite deposits, and could lead to surface deformation over time.

Airborne Instrument Simulator for the Lidar Surface Topography (LIST) Mission

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Krainak, Michael A.; Harding, David J.; Abshire, James B.; Sun, Xiaoli; Cavanaugh, John; Valett, Susan; Ramos-Izquierdo, Luis

2010-01-01

In 2007, the National Research Council (NRC) completed its first decadal survey for Earth science at the request of NASA, NOAA, and USGS. The Lidar Surface Topography (LIST) mission is one of fifteen missions recommended by NRC, whose primary objectives are to map global topography and vegetation structure at 5 m spatial resolution, and to acquire global coverage with a few years. NASA Goddard conducted an initial mission concept study for the LIST mission 2007, and developed the initial measurement requirements for the mission.

3D reconstruction of highly fragmented bone fractures

NASA Astrophysics Data System (ADS)

Willis, Andrew; Anderson, Donald; Thomas, Thad; Brown, Thomas; Marsh, J. Lawrence

2007-03-01

A system for the semi-automatic reconstruction of highly fragmented bone fractures, developed to aid in treatment planning, is presented. The system aligns bone fragment surfaces derived from segmentation of volumetric CT scan data. Each fragment surface is partitioned into intact- and fracture-surfaces, corresponding more or less to cortical and cancellous bone, respectively. A user then interactively selects fracture-surface patches in pairs that coarsely correspond. A final optimization step is performed automatically to solve the N-body rigid alignment problem. The work represents the first example of a 3D bone fracture reconstruction system and addresses two new problems unique to the reconstruction of fractured bones: (1) non-stationary noise inherent in surfaces generated from a difficult segmentation problem and (2) the possibility that a single fracture surface on a fragment may correspond to many other fragments.

ARC-1979-A79-7088

NASA Image and Video Library

1979-07-10

P-21760 BW This color image of the Jovian moon Europa, which is the size of our moon, is thought to have a crust of ice perhaps 100 kilometers thick which overlies the silicate crust. The complex array of streaks indicate that the crust has been fractured and filled by materials from the interior. The lack of relief, any visible mountains or craters, on its bright limb is consistent with a thick ice crust. In contrast to its icy neighbors, Ganymede and Callisto, Europa has very few impact craters. One possible candidate is the small feature near the center of this image with radiating rays and a bright circular interior. The relative absence of features and low topography suggests the crust is young and warm a few kilometers below the surface. The tidal heating process suggested for Io also may be heating Europa's interior at a lower rate.

ARC-1979-AC79-7088

NASA Image and Video Library

1979-07-10

P-21760 C This color image of the Jovian moon Europa, which is the size of our moon, is thought to have a crust of ice perhaps 100 kilometers thick which overlies the silicate crust. The complex array of streaks indicate that the crust has been fractured and filled by materials from the interior. The lack of relief, any visible mountains or craters, on its bright limb is consistent with a thick ice crust. In contrast to its icy neighbors, Ganymede and Callisto, Europa has very few impact craters. One possible candidate is the small feature near the center of this image with radiating rays and a bright circular interior. The relative absence of features and low topography suggests the crust is young and warm a few kilometers below the surface. The tidal heating process suggested for Io also may be heating Europa's interior at a lower rate.

Topography measurements and applications in ballistics and tool mark identifications*

PubMed Central

Vorburger, T V; Song, J; Petraco, N

2016-01-01

The application of surface topography measurement methods to the field of firearm and toolmark analysis is fairly new. The field has been boosted by the development of a number of competing optical methods, which has improved the speed and accuracy of surface topography acquisitions. We describe here some of these measurement methods as well as several analytical methods for assessing similarities and differences among pairs of surfaces. We also provide a few examples of research results to identify cartridge cases originating from the same firearm or tool marks produced by the same tool. Physical standards and issues of traceability are also discussed. PMID:27182440

3D surface topography study of the biofunctionalized nanocrystalline Ti-6Zr-4Nb/Ca-P

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jakubowicz, J., E-mail: jaroslaw.jakubowicz@put.poznan.pl; Adamek, G.; Jurczyk, M.U.

2012-08-15

In this work surface of the sintered Ti-6Zr-4Nb nanocrystalline alloy was electrochemically biofunctionalized. The porous surface was produced by anodic oxidation in 1 M H{sub 3}PO{sub 4} + 2%HF electrolyte at 10 V for 30 min. Next the calcium-phosphate (Ca-P) layer was deposited, onto the formed porous surface, using cathodic potential - 5 V kept for 60 min in 0.042 M Ca(NO{sub 3}){sub 2} + 0.025 M (NH{sub 4}){sub 2}HPO{sub 4} + 0.1 M HCl electrolyte. The deposited Ca-P layer anchored in the pores. The biofunctionalized surface was studied by XRD, SEM and EDS. In vitro tests culture of normalmore » human osteoblast (NHOst) cells showed very good cells proliferation, colonization and multilayering. Using optical profiler, roughness and hybrid 3D surface topography parameters were estimated. Correlation between surface composition, morphology, roughness and biocompatibility results was done. It has been shown by us that surface with appropriate chemical composition and topography, after combined electrochemical anodic and cathodic surface treatment, supports osteoblast adhesion and proliferation. 3D topography measurements using optical profiler play a key role in the biomaterials surface analysis. - Highlights: Black-Right-Pointing-Pointer Nanocrystalline Ti-6Zr-4Nb/Ca-P material was produced for hard tissue implant applications. Black-Right-Pointing-Pointer Calcium-phosphate results in surface biofunctionalization. Black-Right-Pointing-Pointer The biofunctionalized surface shows good in-vitro behavior.« less

Quantitative geometric description of fracture systems in an andesite lava flow using terrestrial laser scanner data

NASA Astrophysics Data System (ADS)

Massiot, Cécile; Nicol, Andrew; Townend, John; McNamara, David D.; Garcia-Sellés, David; Conway, Chris E.; Archibald, Garth

2017-07-01

Permeability hosted in andesitic lava flows is dominantly controlled by fracture systems, with geometries that are often poorly constrained. This paper explores the fracture system geometry of an andesitic lava flow formed during its emplacement and cooling over gentle paleo-topography, on the active Ruapehu volcano, New Zealand. The fracture system comprises column-forming and platy fractures within the blocky interior of the lava flow, bounded by autobreccias partially observed at the base and top of the outcrop. We use a terrestrial laser scanner (TLS) dataset to extract column-forming fractures directly from the point-cloud shape over an outcrop area of ∼3090 m2. Fracture processing is validated using manual scanlines and high-resolution panoramic photographs. Column-forming fractures are either steeply or gently dipping with no preferred strike orientation. Geometric analysis of fractures derived from the TLS, in combination with virtual scanlines and trace maps, reveals that: (1) steeply dipping column-forming fracture lengths follow a scale-dependent exponential or log-normal distribution rather than a scale-independent power-law; (2) fracture intensities (combining density and size) vary throughout the blocky zone but have similar mean values up and along the lava flow; and (3) the areal fracture intensity is higher in the autobreccia than in the blocky zone. The inter-connected fracture network has a connected porosity of ∼0.5 % that promote fluid flow vertically and laterally within the blocky zone, and is partially connected to the autobreccias. Autobreccias may act either as lateral permeability connections or barriers in reservoirs, depending on burial and alteration history. A discrete fracture network model generated from these geometrical parameters yields a highly connected fracture network, consistent with outcrop observations.

Using Measurements of Topography to Infer Rates of Crater Degradation and Surface Evolution on the Moon and Mercury

NASA Technical Reports Server (NTRS)

Fassett, Caleb; Crowley, Lindy; Leight, Clarissa; Dyar, Darby; Minton, David; Hirabayashi, Toshi; Thomson, Brad; Watters, Wesley

2017-01-01

Motivating questions: 1. How does the topography of airless bodies evolve? 2. What is the relative rate on the Moon and Mercury? 3. Can we constrain the age of features and units from their topography?

Application of a pore-scale reactive transport model to a natural analog for reaction-induced pore alterations

DOE PAGES

Yoon, Hongkyu; Major, Jonathan; Dewers, Thomas; ...

2017-01-05

Dissolved CO 2 in the subsurface resulting from geological CO 2 storage may react with minerals in fractured rocks, confined aquifers, or faults, resulting in mineral precipitation and dissolution. The overall rate of reaction can be affected by coupled processes including hydrodynamics, transport, and reactions at the (sub) pore-scale. In this work pore-scale modeling of coupled fluid flow, reactive transport, and heterogeneous reactions at the mineral surface is applied to account for permeability alterations caused by precipitation-induced pore-blocking. This paper is motivated by observations of CO 2 seeps from a natural CO 2 sequestration analog, Crystal Geyser, Utah. Observations alongmore » the surface exposure of the Little Grand Wash fault indicate the lateral migration of CO 2 seep sites (i.e., alteration zones) of 10–50 m width with spacing on the order of ~100 m over time. Sandstone permeability in alteration zones is reduced by 3–4 orders of magnitude by carbonate cementation compared to unaltered zones. One granular porous medium and one fracture network systems are used to conceptually represent permeable porous media and locations of conduits controlled by fault-segment intersections and/or topography, respectively. Simulation cases accounted for a range of reaction regimes characterized by the Damköhler (Da) and Peclet (Pe) numbers. Pore-scale simulation results demonstrate that combinations of transport (Pe), geochemical conditions (Da), solution chemistry, and pore and fracture configurations contributed to match key patterns observed in the field of how calcite precipitation alters flow paths by pore plugging. This comparison of simulation results with field observations reveals mechanistic explanations of the lateral migration and enhances our understanding of subsurface processes associated with the CO 2 injection. In addition, permeability and porosity relations are constructed from pore-scale simulations which account for a range of reaction regimes characterized by the Da and Pe numbers. Finally, the functional relationships obtained from pore-scale simulations can be used in a continuum scale model that may account for large-scale phenomena mimicking lateral migration of surface CO 2 seeps.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoon, Hongkyu; Major, Jonathan; Dewers, Thomas

Dissolved CO 2 in the subsurface resulting from geological CO 2 storage may react with minerals in fractured rocks, confined aquifers, or faults, resulting in mineral precipitation and dissolution. The overall rate of reaction can be affected by coupled processes including hydrodynamics, transport, and reactions at the (sub) pore-scale. In this work pore-scale modeling of coupled fluid flow, reactive transport, and heterogeneous reactions at the mineral surface is applied to account for permeability alterations caused by precipitation-induced pore-blocking. This paper is motivated by observations of CO 2 seeps from a natural CO 2 sequestration analog, Crystal Geyser, Utah. Observations alongmore » the surface exposure of the Little Grand Wash fault indicate the lateral migration of CO 2 seep sites (i.e., alteration zones) of 10–50 m width with spacing on the order of ~100 m over time. Sandstone permeability in alteration zones is reduced by 3–4 orders of magnitude by carbonate cementation compared to unaltered zones. One granular porous medium and one fracture network systems are used to conceptually represent permeable porous media and locations of conduits controlled by fault-segment intersections and/or topography, respectively. Simulation cases accounted for a range of reaction regimes characterized by the Damköhler (Da) and Peclet (Pe) numbers. Pore-scale simulation results demonstrate that combinations of transport (Pe), geochemical conditions (Da), solution chemistry, and pore and fracture configurations contributed to match key patterns observed in the field of how calcite precipitation alters flow paths by pore plugging. This comparison of simulation results with field observations reveals mechanistic explanations of the lateral migration and enhances our understanding of subsurface processes associated with the CO 2 injection. In addition, permeability and porosity relations are constructed from pore-scale simulations which account for a range of reaction regimes characterized by the Da and Pe numbers. Finally, the functional relationships obtained from pore-scale simulations can be used in a continuum scale model that may account for large-scale phenomena mimicking lateral migration of surface CO 2 seeps.« less

Effect of Surface Modifications of Ti40Zr10Cu38Pd12 Bulk Metallic Glass and Ti-6Al-4V Alloy on Human Osteoblasts In Vitro Biocompatibility

PubMed Central

Blanquer, Andreu; Hynowska, Anna; Nogués, Carme; Ibáñez, Elena; Sort, Jordi; Baró, Maria Dolors; Özkale, Berna; Pané, Salvador; Pellicer, Eva

2016-01-01

The use of biocompatible materials, including bulk metallic glasses (BMGs), for tissue regeneration and transplantation is increasing. The good mechanical and corrosion properties of Ti40Zr10Cu38Pd12 BMG and its previously described biocompatibility makes it a potential candidate for medical applications. However, it is known that surface properties like topography might play an important role in regulating cell adhesion, proliferation and differentiation. Thus, in the present study, Ti40Zr10Cu38Pd12 BMG and Ti6-Al-4V alloy were surface-modified electrochemically (nanomesh) or physically (microscratched) to investigate the effect of material topography on human osteoblasts cells (Saos-2) adhesion, proliferation and differentiation. For comparative purposes, the effect of mirror-like polished surfaces was also studied. Electrochemical treatments led to a highly interconnected hierarchical porous structure rich in oxides, which have been described to improve corrosion resistance, whereas microscratched surfaces showed a groove pattern with parallel trenches. Cell viability was higher than 96% for the three topographies tested and for both alloy compositions. In all cases, cells were able to adhere, proliferate and differentiate on the alloys, hence indicating that surface topography plays a minor role on these processes, although a clear cell orientation was observed on microscratched surfaces. Overall, our results provide further evidence that Ti40Zr10Cu38Pd12 BMG is an excellent candidate, in the present two topographies, for bone repair purposes. PMID:27243628

Early human bone response to laser metal sintering surface topography: a histologic report.

PubMed

Mangano, Carlo; Piattelli, Adriano; d'Avila, Susana; Iezzi, Giovanna; Mangano, Francesco; Onuma, Tatiana; Shibli, Jamil Awad

2010-01-01

This histologic report evaluated the early human bone response to a direct laser metal sintering implant surface retrieved after a short period of healing. A selective laser sintering procedure using a Ti-6Al-4V alloy powder with a particle size of 25-45 microm prepared this surface topography. One experimental microimplant was inserted into the anterior mandible of a patient during conventional implant surgery of the jaw. The microimplant and surrounding tissues were removed after 2 months of unloaded healing and were prepared for histomorphometric analysis. Histologically, the peri-implant bone appeared in close contact with the implant surface, whereas marrow spaces could be detected in other areas along with prominently stained cement lines. The mean of bone-to-implant contact was 69.51%. The results of this histologic report suggest that the laser metal sintering surface could be a promising alternative to conventional implant surface topographies.

Surface texture measurement for dental wear applications

NASA Astrophysics Data System (ADS)

Austin, R. S.; Mullen, F.; Bartlett, D. W.

2015-06-01

The application of surface topography measurement and characterization within dental materials science is highly active and rapidly developing, in line with many modern industries. Surface measurement and structuring is used extensively within oral and dental science to optimize the optical, tribological and biological performance of natural and biomimetic dental materials. Although there has historically been little standardization in the use and reporting of surface metrology instrumentation and software, the dental industry is beginning to adopt modern areal measurement and characterization techniques, especially as the dental industry is increasingly adopting digital impressioning techniques in order to leverage CAD/CAM technologies for the design and construction of dental restorations. As dental treatment becomes increasingly digitized and reliant on advanced technologies such as dental implants, wider adoption of standardized surface topography and characterization techniques will become evermore essential. The dental research community welcomes the advances that are being made in surface topography measurement science towards realizing this ultimate goal.

Mining for osteogenic surface topographies: In silico design to in vivo osseo-integration.

PubMed

Hulshof, Frits F B; Papenburg, Bernke; Vasilevich, Aliaksei; Hulsman, Marc; Zhao, Yiping; Levers, Marloes; Fekete, Natalie; de Boer, Meint; Yuan, Huipin; Singh, Shantanu; Beijer, Nick; Bray, Mark-Anthony; Logan, David J; Reinders, Marcel; Carpenter, Anne E; van Blitterswijk, Clemens; Stamatialis, Dimitrios; de Boer, Jan

2017-08-01

Stem cells respond to the physicochemical parameters of the substrate on which they grow. Quantitative material activity relationships - the relationships between substrate parameters and the phenotypes they induce - have so far poorly predicted the success of bioactive implant surfaces. In this report, we screened a library of randomly selected designed surface topographies for those inducing osteogenic differentiation of bone marrow-derived mesenchymal stem cells. Cell shape features, surface design parameters, and osteogenic marker expression were strongly correlated in vitro. Furthermore, the surfaces with the highest osteogenic potential in vitro also demonstrated their osteogenic effect in vivo: these indeed strongly enhanced bone bonding in a rabbit femur model. Our work shows that by giving stem cells specific physicochemical parameters through designed surface topographies, differentiation of these cells can be dictated. Copyright © 2017 Elsevier Ltd. All rights reserved.

Full-field measurement of surface topographies and thin film stresses at elevated temperatures by digital gradient sensing method.

PubMed

Zhang, Changxing; Qu, Zhe; Fang, Xufei; Feng, Xue; Hwang, Keh-Chih

2015-02-01

Thin film stresses in thin film/substrate systems at elevated temperatures affect the reliability and safety of such structures in microelectronic devices. The stresses result from the thermal mismatch strain between the film and substrate. The reflection mode digital gradient sensing (DGS) method, a real-time, full-field optical technique, measures deformations of reflective surface topographies. In this paper, we developed this method to measure topographies and thin film stresses of thin film/substrate systems at elevated temperatures. We calibrated and compensated for the air convection at elevated temperatures, which is a serious problem for optical techniques. We covered the principles for surface topography measurements by the reflection mode DGS method at elevated temperatures and the governing equations to remove the air convection effects. The proposed method is applied to successfully measure the full-field topography and deformation of a NiTi thin film on a silicon substrate at elevated temperatures. The evolution of thin film stresses obtained by extending Stoney's formula implies the "nonuniform" effect the experimental results have shown.

Human Corneal Limbal-Epithelial Cell Response to Varying Silk Film Geometric Topography In Vitro

PubMed Central

Lawrence, Brian D.; Pan, Zhi; Liu, Aihong; Kaplan, David L.; Rosenblatt, Mark I.

2012-01-01

Silk fibroin films are a promising class of biomaterials that have a number of advantages for use in ophthalmic applications due to their transparent nature, mechanical properties and minimal inflammatory response upon implantation. Freestanding silk films with parallel line and concentric ring topographies were generated for in vitro characterization of human corneal limbal-epithelial (HCLE) cell response upon differing geometric patterned surfaces. Results indicated that silk film topography significantly affected initial HCLE culture substrate attachment, cellular alignment, cell-to-cell contact formation, actin cytoskeleton alignment, and focal adhesion (FA) localization. Most notably, parallel line patterned surfaces displayed a 36%–54% increase on average in initial cell attachment, which corresponded to an over 2-fold increase in FA localization when compared to other silk film surfaces and controls. In addition, distinct localization of FA formation was observed along the edges for all patterned silk film topographies. In conclusion, silk film feature topography appears to help direct corneal epithelial cell response and cytoskeleton development, especially in regards to FA distribution, in vitro. PMID:22705042

Photometric stereo endoscopy.

PubMed

Parot, Vicente; Lim, Daryl; González, Germán; Traverso, Giovanni; Nishioka, Norman S; Vakoc, Benjamin J; Durr, Nicholas J

2013-07-01

While color video endoscopy has enabled wide-field examination of the gastrointestinal tract, it often misses or incorrectly classifies lesions. Many of these missed lesions exhibit characteristic three-dimensional surface topographies. An endoscopic system that adds topographical measurements to conventional color imagery could therefore increase lesion detection and improve classification accuracy. We introduce photometric stereo endoscopy (PSE), a technique which allows high spatial frequency components of surface topography to be acquired simultaneously with conventional two-dimensional color imagery. We implement this technique in an endoscopic form factor and demonstrate that it can acquire the topography of small features with complex geometries and heterogeneous optical properties. PSE imaging of ex vivo human gastrointestinal tissue shows that surface topography measurements enable differentiation of abnormal shapes from surrounding normal tissue. Together, these results confirm that the topographical measurements can be obtained with relatively simple hardware in an endoscopic form factor, and suggest the potential of PSE to improve lesion detection and classification in gastrointestinal imaging.

Elucidating Dynamical Processes Relevant to Flow Encountering Abrupt Topography (FLEAT)

DTIC Science & Technology

2015-09-30

Encountering Abrupt Topography (FLEAT) Bo Qiu Dept of Oceanography, University of Hawaii at Manoa 1000 Pope Rd. Honolulu, HI 96822 phone: (808) 956...c) to explore relevant dynamics by using both simplified models and OGCM output with realistic topography and surface boundary conditions...scale abyssal circulation, we propose to use the Hallberg Isopycnal Model (HIM). The HIM allows sloping isopycnals to interact with bottom topography

Allometric scaling of infraorbital surface topography in Homo.

PubMed

Maddux, Scott D; Franciscus, Robert G

2009-02-01

Infraorbital morphology is often included in phylogenetic and functional analyses of Homo. The inclusion of distinct infraorbital configurations, such as the "canine fossa" in Homo sapiens or the "inflated" maxilla in Neandertals, is generally based on either descriptive or qualitative assessments of this morphology, or simple linear chord and subtense measurements. However, the complex curvilinear surface of the infraorbital region has proven difficult to quantify through these traditional methods. In this study, we assess infraorbital shape and its potential allometric scaling in fossil Homo (n=18) and recent humans (n=110) with a geometric morphometric method well-suited for quantifying complex surface topographies. Our results indicate that important aspects of infraorbital shape are correlated with overall infraorbital size across Homo. Specifically, individuals with larger infraorbital areas tend to exhibit relatively flatter infraorbital surface topographies, taller and narrower infraorbital areas, sloped inferior orbital rims, anteroinferiorly oriented maxillary body facies, posteroinferiorly oriented maxillary processes of the zygomatic, and non-everted lateral nasal margins. In contrast, individuals with smaller infraorbital regions generally exhibit relatively depressed surface topographies, shorter and wider infraorbital areas, projecting inferior orbital rims, posteroinferiorly oriented maxillary body facies, anteroinferiorly oriented maxillary processes, and everted lateral nasal margins. These contrasts form a continuum and only appear dichotomized at the ends of the infraorbital size spectrum. In light of these results, we question the utility of incorporating traditionally polarized infraorbital morphologies in phylogenetic and functional analyses without due consideration of continuous infraorbital and facial size variation in Homo. We conclude that the essentially flat infraorbital surface topography of Neandertals is not unique and can be explained, in part, as a function of possessing large infraorbital regions, the ancestral condition for Homo. Furthermore, it appears likely that the diminutive infraorbital region of anatomically modern Homo sapiens is a primary derived trait, with related features such as depressed infraorbital surface topography expressed as correlated secondary characters.

White Light Used to Enable Enhanced Surface Topography, Geometry, and Wear Characterization of Oil-Free Bearings

NASA Technical Reports Server (NTRS)

Lucero, John M.

2003-01-01

A new optically based measuring capability that characterizes surface topography, geometry, and wear has been employed by NASA Glenn Research Center s Tribology and Surface Science Branch. To characterize complex parts in more detail, we are using a three-dimensional, surface structure analyzer-the NewView5000 manufactured by Zygo Corporation (Middlefield, CT). This system provides graphical images and high-resolution numerical analyses to accurately characterize surfaces. Because of the inherent complexity of the various analyzed assemblies, the machine has been pushed to its limits. For example, special hardware fixtures and measuring techniques were developed to characterize Oil- Free thrust bearings specifically. We performed a more detailed wear analysis using scanning white light interferometry to image and measure the bearing structure and topography, enabling a further understanding of bearing failure causes.

Effects of various etching protocols on the flexural properties and surface topography of fiber-reinforced composite dental posts.

PubMed

Aksornmuang, Juthatip; Chuenarrom, Chanya; Chittithaworn, Natjira

2017-09-26

The purpose of this study was to evaluate the flexural properties and surface topography of fiber posts surface-treated with various etching protocols. Seventy each of three types of fiber posts: RelyX Fiber Post, Tenax Fiber Trans, and D.T. Light-Post Illusion X-Ro, were randomly divided into 7 groups: no surface treatment, surface treated with hydrofluoric acid (HF) 4.5% for 60 s, HF 4.5% for 120 s, HF 9.6% for 15 s, HF 9.6% for 60 s, HF 9.6% for 120 s, and treated with H 2 O 2 24% for 10 min. The specimens were then subjected to a three-point bending test. Surface topographies of the posts were observed using a SEM. The results indicate that fiber post surface pretreatments had no adverse effects on the flexural properties. However, the fiber posts treated with high HF concentrations or long etching times seemed to have more surface irregularities.

Structure of a seismogenic fault zone in dolostones: the Foiana Line (Italian Southern Alps)

NASA Astrophysics Data System (ADS)

Di Toro, G.; Fondriest, M.; Smith, S. A.; Aretusini, S.

2012-12-01

Fault zones in carbonate rocks (limestones and dolostones) represent significant upper crustal seismogenic sources in several areas worldwide (e.g. L'Aquila 2009 Mw = 6.3 in central Italy). Here we describe an exhumed example of a regionally-significant fault zone cutting dolostones. The Foiana Line (FL) is a major NNE-SSW-trending sinistral transpressive fault cutting sedimentary Triassic dolostones in the Italian Southern Alps. The FL has a cumulative vertical throw of 1.5-2 km that reduces toward its southern termination. The fault zone is 50-300 m wide and is exposed for ~ 10 km along strike within several outcrops exhumed from increasing depths from the south (1 km) to the north (2.5 km). The southern portion of the FL consists of heavily fractured (shattered) dolostones, with particles of a few millimeters in size (exposed in badlands topography over an area of 6 km2), cut by a dense network of 1-20 m long mirror-like fault surfaces with dispersed attitudes. The mirror-like faults have mainly dip-slip reverse kinematics and displacements ranging between 0.04 m and 0.5 m. The northern portion of the FL consists of sub-parallel fault strands spaced 2-5 m apart, surrounded by 2-3 m thick bands of shattered dolostones. The fault strands are characterized by smooth to mirror-like sub-vertical slip surfaces with dominant strike-slip kinematics. Overall, deformation is more localized moving from South to North along the FL. Mirror-like fault surfaces similar to those found in the FL were produced in friction experiments at the deformation conditions expected during seismic slip along the FL (Fondriest et al., this meeting). Scanning Electron Microscope investigations of the natural shattered dolostones beneath the mirror-like fault surfaces show: 1) lack of significant shear strain (even at a few micrometers from the slip surface), 2) pervasive extensional fracturing down to the micrometer scale, 3) exploded clasts with radial fractures, and 4) chains of split clasts (resulting from force chains) oriented at 60-80 degrees to the slip surfaces. Similar features have been reported in natural and experimental pulverized rocks, the latter produced under dynamic stress wave loading conditions. 3-Dimensional rupture simulations along strike-slip faults predict (1) off-fault damage distributions with "flower-like" shapes (broad damage zone near the surface that rapidly narrows with increasing confining pressure, e.g., Ma and Andrews, 2010) and (2) formation of secondary faults/fractures with disperse attitudes and kinematics near the surface, with horizontal slip at depth. Qualitatively, these theoretical results compare favorably with increasing strain localization and a switch in fault kinematics recognized along the FL moving from the southern, shallower portion of the fault zone to the northern, deeper portion. Observations along the FL suggest that the association of shattered dolostones and mirror-like slip surfaces might be a potential indicator of seismic rupture propagation. Further detailed structural mapping along the FL coupled with experimental work on rock pulverization will be necessary to understand rupture dynamics in dolostones.

Elastic Reverse Time Migration (RTM) From Surface Topography

NASA Astrophysics Data System (ADS)

Akram, Naveed; Chen, Xiaofei

2017-04-01

Seismic Migration is a promising data processing technique to construct subsurface images by projecting the recorded seismic data at surface back to their origins. There are numerous Migration methods. Among them, Reverse Time Migration (RTM) is considered a robust and standard imaging technology in present day exploration industry as well as in academic research field because of its superior performance compared to traditional migration methods. Although RTM is extensive computing and time consuming but it can efficiently handle the complex geology, highly dipping reflectors and strong lateral velocity variation all together. RTM takes data recorded at the surface as a boundary condition and propagates the data backwards in time until the imaging condition is met. It can use the same modeling algorithm that we use for forward modeling. The classical seismic exploration theory assumes flat surface which is almost impossible in practice for land data. So irregular surface topography has to be considered in simulation of seismic wave propagation, which is not always a straightforward undertaking. In this study, Curved grid finite difference method (CG-FDM) is adapted to model elastic seismic wave propagation to investigate the effect of surface topography on RTM results and explore its advantages and limitations with synthetic data experiments by using Foothill model with topography as the true model. We focus on elastic wave propagation rather than acoustic wave because earth actually behaves as an elastic body. Our results strongly emphasize on the fact that irregular surface topography must be considered for modeling of seismic wave propagation to get better subsurface images specially in mountainous scenario and suggest practitioners to properly handled the geometry of data acquired on irregular topographic surface in their imaging algorithms.

Elastic Reverse Time Migration (RTM) From Surface Topography

NASA Astrophysics Data System (ADS)

Naveed, A.; Chen, X.

2016-12-01

Seismic Migration is a promising data processing technique to construct subsurface images by projecting the recorded seismic data at surface back to their origins. There are numerous Migration methods. Among them, Reverse Time Migration (RTM) is considered a robust and standard imaging technology in present day exploration industry as well as in academic research field because of its superior performance compared to traditional migration methods. Although RTM is extensive computing and time consuming but it can efficiently handle the complex geology, highly dipping reflectors and strong lateral velocity variation all together. RTM takes data recorded at the surface as a boundary condition and propagates the data backwards in time until the imaging condition is met. It can use the same modeling algorithm that we use for forward modeling. The classical seismic exploration theory assumes flat surface which is almost impossible in practice for land data. So irregular surface topography has to be considered in simulation of seismic wave propagation, which is not always a straightforward undertaking. In this study, Curved grid finite difference method (CG-FDM) is adapted to model elastic seismic wave propagation to investigate the effect of surface topography on RTM results and explore its advantages and limitations with synthetic data experiments by using Foothill model with topography as the true model. We focus on elastic wave propagation rather than acoustic wave because earth actually behaves as an elastic body. Our results strongly emphasize on the fact that irregular surface topography must be considered for modeling of seismic wave propagation to get better subsurface images specially in mountainous scenario and suggest practitioners to properly handled the geometry of data acquired on irregular topographic surface in their imaging algorithms.

The Comprehensive AOCMF Classification System: Midface Fractures - Level 3 Tutorial

PubMed Central

Cornelius, Carl-Peter; Audigé, Laurent; Kunz, Christoph; Buitrago-Téllez, Carlos H.; Rudderman, Randal; Prein, Joachim

2014-01-01

This tutorial outlines the details of the AOCMF image-based classification system for fractures of the midface at the precision level 3. The topography of the different midface regions (central midface—upper central midface, intermediate central midface, lower central midface—incorporating the naso-orbito-ethmoid region; lateral midface—zygoma and zygomatic arch, palate) is subdivided in much greater detail than in level 2 going beyond the Le Fort fracture types and its analogs. The level 3 midface classification system is presented along with guidelines to precisely delineate the fracture patterns in these specific subregions. It is easy to plot common fracture entities, such as nasal and naso-orbito-ethmoid, and their variants due to the refined structural layout of the subregions. As a key attribute, this focused approach permits to document the occurrence of fragmentation (i.e., single vs. multiple fracture lines), displacement, and bone loss. Moreover, the preinjury dental state and the degree of alveolar atrophy in edentulous maxillary regions can be recorded. On the basis of these individual features, tooth injuries, periodontal trauma, and fracture involvement of the alveolar process can be assessed. Coding rules are given to set up a distinctive formula for typical midface fractures and their combinations. The instructions and illustrations are elucidated by a series of radiographic imaging examples. A critical appraisal of the design of this level 3 midface classification is made. PMID:25489392

Sedimentation in the Kane fracture zone, western North Atlantic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaroslow, G.E.

1991-03-01

The Kane fracture zone, a deep narrow trough in oceanic crust, has provided an ideal depocenter for reservation on the seismic stratigraphic record of the North Atlantic basin. The acoustic stratigraphy in single-channel and multichannel seismic reflection profiles crossing the Kane fracture zone in the western North Atlantic has been examined in order to scrutinize age processes within a fracture zone. Maps of total sediment thickness have provided insight into overall sediment distribution and the influence of topography on sedimentation. Eight reflectors have been traced and correlated with lithostratigraphy at Deep Sea Drilling Project (DSDP) sites. The Bermuda Rise, amore » prominent topographic feature, has had a profound effect on the distribution of sediments within the fracture zone. Since late Eocene, the rise has blocked transport by turbidity currents of terrigenous sediments to distal portions of the fracture valley. A 1,000-m-thick turbidite pond within the fracture zone east of the Bermuda Rise has been determined to have been derived from local sources. Within the ponded sequence a seismic discontinuity is estimated to be early Oligocene and postdates the emergence of the Bermuda Rise, adding an independent age constraint on the development of the rise. The pond terminates against a structural dam at 55{degree}20W, east of which the fracture zone is essentially sediment starved.« less

Spatial distribution of erosion in the Hangay Mountains of Mongolia and implications for the development of epeirogenic topography

NASA Astrophysics Data System (ADS)

West, A.; Fox, M.; Walker, R. T.; Carter, A.; Watts, A. B.; Gantulga, B.

2012-12-01

Potential feedbacks between climate-driven erosion and the development of intra-continental topography have received relatively little attention, particularly compared to the significant efforts to understand the interplay of climate, erosion, and uplift in orogenic settings. But such links may be vital for understanding the topographic evolution of epeirogenic topography and for making inferences about geodynamic processes based on associated sedimentary and geomorphic signals. In this study, we consider the role of orographically-driven climate variability in shaping continental topography by focusing on the Hangay mountain range, a uplifted dome in central Mongolia. The work presented here is based on results from a topographic analysis of the Hangay, making use of the flat-topped peaks that effectively represent preserved remnants of a pre-erosional surface. We have determined the scale and distribution of erosion by recreating this pre-erosional surface and subtracting the present-day, dissected topography. Our results show that the extent of erosion correlates with spatial variation in mean annual precipitation, but not with the extent of total surface uplift. The morphology of the range reflects the higher, climate-driven fluvial erosion rates by northern rivers that receive higher precipitation when compared to the southern rivers, which have steeper relief as a result of the asymmetric main drainage divide. Overall asymmetry in inferred isostatic response to erosional unloading is not mirrored in asymmetry of total surface uplift, hinting at interaction between surface erosion and the forces sustaining topography. This has important implications for understanding the geodynamics of epeirogenic uplift. In addition to these main outcomes from our topographic analysis, we will also present preliminary findings from detrital thermochronology and cosmogenic analyses that help to pinpoint the location of erosion and provide a basis for quantifying rates.

Organic pi-stacking Semiconducting Material: Design, Synthesis and the Analysis of Structure and Properties

NASA Astrophysics Data System (ADS)

Wilkinson, Taylor Marie

Oil shales are naturally occurring heterogeneous composites with micro-scale, micro-structural variations. They may be found throughout the world, with large deposits located in the United States; shales are composed of organic matter known as kerogen, clays, calcite, quartz, and other minerals. Typically their microstructure consists of a composite network where the organic matter is housed in open and closed pores between different mineral phases that range in size from sub-micron to several microns. Currently, it is unknown how the micro-scale heterogeneity of the shale will impact hydraulic fracture, which is the key extraction technique used for these materials. In this thesis, high-resolution topographic and modulus maps were collected from oil shales with the use of new nanoindentation techniques in order to characterize the micro-scale, micro-structural variations that are typical for these materials. Dynamic modulus mapping allows for substantially higher spatial resolution of properties across grains and intragranular regions of kerogen than has previously been produced with standard quasistatic indentation methods. For accurate scanning, surface variations were minimized to maintain uniform contact of the tip and appropriate quasi-static and dynamic forces were used to maintain displacement amplitudes that avoid plastic deformation of the sample. Sample preparation to minimize surface roughness was completed with the use of focused ion beam milling, however, some variation was still noted. Due to the large changes in modulus values between the constituents of the shale, there were variations in the recorded displacement amplitude values as well. In order to distinguish biased data due to surface topography or a lack of displacement amplitude, filtering techniques were developed, optimization and implemented. Variations in surface topography, which resulted in the indenter tip not being able to accurately resolve surface features, and inadequate displacement amplitude values that prohibit differentiation between material changes and the noise floor of the machine, were removed. These filters resulted in a more valid interpretation of the micro-scale, micro-structural features and arrangement, as well as the mechanical properties, that are common to oil shales.

Coupling 3D groundwater modeling with CFC-based age dating to classify local groundwater circulation in an unconfined crystalline aquifer

NASA Astrophysics Data System (ADS)

Kolbe, Tamara; Marçais, Jean; Thomas, Zahra; Abbott, Benjamin W.; de Dreuzy, Jean-Raynald; Rousseau-Gueutin, Pauline; Aquilina, Luc; Labasque, Thierry; Pinay, Gilles

2016-12-01

Nitrogen pollution of freshwater and estuarine environments is one of the most urgent environmental crises. Shallow aquifers with predominantly local flow circulation are particularly vulnerable to agricultural contaminants. Water transit time and flow path are key controls on catchment nitrogen retention and removal capacity, but the relative importance of hydrogeological and topographical factors in determining these parameters is still uncertain. We used groundwater dating and numerical modeling techniques to assess transit time and flow path in an unconfined aquifer in Brittany, France. The 35.5 km2 study catchment has a crystalline basement underneath a ∼60 m thick weathered and fractured layer, and is separated into a distinct upland and lowland area by an 80 m-high butte. We used groundwater discharge and groundwater ages derived from chlorofluorocarbon (CFC) concentration to calibrate a free-surface flow model simulating groundwater flow circulation. We found that groundwater flow was highly local (mean travel distance = 350 m), substantially smaller than the typical distance between neighboring streams (∼1 km), while CFC-based ages were quite old (mean = 40 years). Sensitivity analysis revealed that groundwater travel distances were not sensitive to geological parameters (i.e. arrangement of geological layers and permeability profile) within the constraints of the CFC age data. However, circulation was sensitive to topography in the lowland area where the water table was near the land surface, and to recharge rate in the upland area where water input modulated the free surface of the aquifer. We quantified these differences with a local groundwater ratio (rGW-LOCAL), defined as the mean groundwater travel distance divided by the mean of the reference surface distances (the distance water would have to travel across the surface of the digital elevation model). Lowland, rGW-LOCAL was near 1, indicating primarily topographical controls. Upland, rGW-LOCAL was 1.6, meaning the groundwater recharge area is almost twice as large as the topographically-defined catchment for any given point. The ratio rGW-LOCAL is sensitive to recharge conditions as well as topography and it could be used to compare controls on groundwater circulation within or between catchments.

Geometry of surface fractures along the Mervine Anticline in Kay County, north central Oklahoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hobbs, R.D.; Cemen, I.; Rizer, W.D.

1993-02-01

Surface fractures in the Lower Permian Barneston Formation are well exposed at three quarries in Kay County, north central Oklahoma. The three quarries are located along the Mervine Anticline which is a broad, assymmetric, low amplitude drape-like fold over a N20E trending sub-surface fault. The most northerly of the three quarries is at the axial surface trace of the anticline. The second quarry is one mile to the west and the third quarry is one-quarter mile to the east of the axial surface trace. In each quarry, a representative area of about 7,850 square feet was chosen for detailed mappingmore » of the surface fractures. In each representative area, the authors divided the surface fractures into what they termed as primary' and secondary' fractures. Traverse and area sampling methods were used to collect quantitative data on the joint orientation and frequency. The primary fractures are orthogonal and have a visible opening, while the secondary fractures have little or no opening. The primary fractures, the orthogonal sets, strike N30W and N75E. The secondary fractures show a slight preferred orientation along N65E although the overall distribution is random. These observations suggest that a similar fracture geometry exists in all three quarries. However, in one quarry the authors observed that fracture surfaces of the N30W striking set are inclined and their formation may have been influenced by movement along the proposed subsurface fault in the area.« less

Insect Wing Membrane Topography Is Determined by the Dorsal Wing Epithelium

PubMed Central

Belalcazar, Andrea D.; Doyle, Kristy; Hogan, Justin; Neff, David; Collier, Simon

2013-01-01

The Drosophila wing consists of a transparent wing membrane supported by a network of wing veins. Previously, we have shown that the wing membrane cuticle is not flat but is organized into ridges that are the equivalent of one wing epithelial cell in width and multiple cells in length. These cuticle ridges have an anteroposterior orientation in the anterior wing and a proximodistal orientation in the posterior wing. The precise topography of the wing membrane is remarkable because it is a fusion of two independent cuticle contributions from the dorsal and ventral wing epithelia. Here, through morphological and genetic studies, we show that it is the dorsal wing epithelium that determines wing membrane topography. Specifically, we find that wing hair location and membrane topography are coordinated on the dorsal, but not ventral, surface of the wing. In addition, we find that altering Frizzled Planar Cell Polarity (i.e., Fz PCP) signaling in the dorsal wing epithelium alone changes the membrane topography of both dorsal and ventral wing surfaces. We also examined the wing morphology of two model Hymenopterans, the honeybee Apis mellifera and the parasitic wasp Nasonia vitripennis. In both cases, wing hair location and wing membrane topography are coordinated on the dorsal, but not ventral, wing surface, suggesting that the dorsal wing epithelium also controls wing topography in these species. Because phylogenomic studies have identified the Hymenotera as basal within the Endopterygota family tree, these findings suggest that this is a primitive insect character. PMID:23316434

Method and Apparatus for Creating a Topography at a Surface

DOEpatents

Adams, David P.; Sinclair, Michael B.; Mayer, Thomas M.; Vasile, Michael J.; Sweatt, William C.

2008-11-11

Methods and apparatus whereby an optical interferometer is utilized to monitor and provide feedback control to an integrated energetic particle column, to create desired topographies, including the depth, shape and/or roughness of features, at a surface of a specimen. Energetic particle columns can direct energetic species including, ions, photons and/or neutral particles to a surface to create features having in-plane dimensions on the order of 1 micron, and a height or depth on the order of 1 nanometer. Energetic processes can include subtractive processes such as sputtering, ablation, focused ion beam milling and, additive processes, such as energetic beam induced chemical vapor deposition. The integration of interferometric methods with processing by energetic species offers the ability to create desired topographies at surfaces, including planar and curved shapes.

Lunar and Planetary Science XXXV: Venus

NASA Technical Reports Server (NTRS)

2004-01-01

The session"Venus" included the following reports:Venera-Vega Geochemical Analyses: What Geologic Units are the Source of the Analyzed Material?; Mapping of Rift Zones on Venus, Preliminary Results: Spatial Distribution, Relationship with Regional Plains, Morphology of Fracturing, Topography and Style of Volcanism; An Effect of Stimulated Radiation Processes on Radio Emission from Major Planets; and Venusian Craters and the Origin of Coronae.

Natural fracture systems on planetary surfaces: Genetic classification and pattern randomness

NASA Technical Reports Server (NTRS)

Rossbacher, Lisa A.

1987-01-01

One method for classifying natural fracture systems is by fracture genesis. This approach involves the physics of the formation process, and it has been used most frequently in attempts to predict subsurface fractures and petroleum reservoir productivity. This classification system can also be applied to larger fracture systems on any planetary surface. One problem in applying this classification system to planetary surfaces is that it was developed for ralatively small-scale fractures that would influence porosity, particularly as observed in a core sample. Planetary studies also require consideration of large-scale fractures. Nevertheless, this system offers some valuable perspectives on fracture systems of any size.

Fractures on Europa - Possible response of an ice crust to tidal deformation

NASA Technical Reports Server (NTRS)

Helfenstein, P.; Parmentier, E. M.

1980-01-01

The surface of Europa contains a planetwide system of low albedo lineaments which have been interpreted as fractures in an icy crust. The pattern of fractures on the surface consists of radial and concentric fractures having the general appearance of tension cracks within a region near the antipode of the sub-Jupiter point. Outside this region, linear fractures intersect at angles near 60 deg, suggesting that they are conjugate shear fractures. The orientation of this pattern on the surface suggests that a principal axis of the deformation that produced the fractures was approximately radial to Jupiter. Fracturing may thus be consistent with an origin due to cyclical tidal deformation resulting from orbital eccentricity. Orbital eccentricity related to a relatively recent establishment of orbital resonance among the Galilean satellites may explain the presence of fractures in a relatively young, lightly cratered planetary surface.

Dynamic Topography Revisited

NASA Astrophysics Data System (ADS)

Moresi, Louis

2015-04-01

Dynamic Topography Revisited Dynamic topography is usually considered to be one of the trinity of contributing causes to the Earth's non-hydrostatic topography along with the long-term elastic strength of the lithosphere and isostatic responses to density anomalies within the lithosphere. Dynamic topography, thought of this way, is what is left over when other sources of support have been eliminated. An alternate and explicit definition of dynamic topography is that deflection of the surface which is attributable to creeping viscous flow. The problem with the first definition of dynamic topography is 1) that the lithosphere is almost certainly a visco-elastic / brittle layer with no absolute boundary between flowing and static regions, and 2) the lithosphere is, a thermal / compositional boundary layer in which some buoyancy is attributable to immutable, intrinsic density variations and some is due to thermal anomalies which are coupled to the flow. In each case, it is difficult to draw a sharp line between each contribution to the overall topography. The second definition of dynamic topography does seem cleaner / more precise but it suffers from the problem that it is not measurable in practice. On the other hand, this approach has resulted in a rich literature concerning the analysis of large scale geoid and topography and the relation to buoyancy and mechanical properties of the Earth [e.g. refs 1,2,3] In convection models with viscous, elastic, brittle rheology and compositional buoyancy, however, it is possible to examine how the surface topography (and geoid) are supported and how different ways of interpreting the "observable" fields introduce different biases. This is what we will do. References (a.k.a. homework) [1] Hager, B. H., R. W. Clayton, M. A. Richards, R. P. Comer, and A. M. Dziewonski (1985), Lower mantle heterogeneity, dynamic topography and the geoid, Nature, 313(6003), 541-545, doi:10.1038/313541a0. [2] Parsons, B., and S. Daly (1983), The relationship between surface topography, gravity anomalies, and temperature structure of convection, Journal of Geophysical Research: Solid Earth (1978-2012), 88(B2), 1129-1144, doi:10.1029/JB088iB02p01129. [3] Robinson, E. M., B. Parsons, and S. F. Daly (1987), The effect of a shallow low viscosity zone on the apparent compensation of mid-plate swells, Earth and Planetary Science Letters, 82(3-4), 335-348, doi:10.1016/0012-821X(87)90207-X.

Multiscale analysis of replication technique efficiency for 3D roughness characterization of manufactured surfaces

NASA Astrophysics Data System (ADS)

Jolivet, S.; Mezghani, S.; El Mansori, M.

2016-09-01

The replication of topography has been generally restricted to optimizing material processing technologies in terms of statistical and single-scale features such as roughness. By contrast, manufactured surface topography is highly complex, irregular, and multiscale. In this work, we have demonstrated the use of multiscale analysis on replicates of surface finish to assess the precise control of the finished replica. Five commercial resins used for surface replication were compared. The topography of five standard surfaces representative of common finishing processes were acquired both directly and by a replication technique. Then, they were characterized using the ISO 25178 standard and multiscale decomposition based on a continuous wavelet transform, to compare the roughness transfer quality at different scales. Additionally, atomic force microscope force modulation mode was used in order to compare the resins’ stiffness properties. The results showed that less stiff resins are able to replicate the surface finish along a larger wavelength band. The method was then tested for non-destructive quality control of automotive gear tooth surfaces.

Micro-Topographies Promote Late Chondrogenic Differentiation Markers in the ATDC5 Cell Line.

PubMed

Le, Bach Q; Vasilevich, Aliaksei; Vermeulen, Steven; Hulshof, Frits; Stamatialis, Dimitrios F; van Blitterswijk, Clemens A; de Boer, Jan

2017-05-01

Chemical and mechanical cues are well-established influencers of in vitro chondrogenic differentiation of ATDC5 cells. Here, we investigate the role of topographical cues in this differentiation process, a study not been explored before. Previously, using a library of surface micro-topographies we found some distinct patterns that induced alkaline phosphatase (ALP) production in human mesenchymal stromal cells. ALP is also a marker for hypertrophy, the end stage of chondrogenic differentiation preceding bone formation. Thus, we hypothesized that these patterns could influence end-stage chondrogenic differentiation of ATDC5 cells. In this study, we randomly selected seven topographies among the ALP influencing hits. Cells grown on these surfaces displayed varying nuclear shape and actin filament structure. When stimulated with insulin-transferrin-selenium (ITS) medium, nodule formation occurred and in some cases showed alignment to the topographical patterns. Gene expression analysis of cells growing on topographical surfaces in the presence of ITS medium revealed a downregulation of early markers and upregulation of late markers of chondrogenic differentiation compared to cells grown on a flat surface. In conclusion, we demonstrated that surface topography in addition to other cues can promote hypertrophic differentiation suitable for bone tissue engineering.

Viscoelastic Relaxation of Topographic Highs on Venus to Produce Coronae

NASA Technical Reports Server (NTRS)

Janes, Daniel M.; Squyres, Steven W.

1995-01-01

Coronae on Venus are believed to result from the gravitationally driven relaxation of topography that was originally raised by mantle diapirs. We examine this relaxation using a viscoelastic finite element code, and show that an initially plateau shaped load will evolve to the characteristic corona topography of central raised bowl, annular rim, and surrounding moat. Stresses induced by the relaxation are consistent with the development of concentric extensional fracturing common on the outer margins of corona moats. However, relaxation is not expected to produce the concentric faulting often observed on the annular rim. The relaxation timescale is shorter than the diapir cooling timescale, so loss of thermal support controls the rate at which topography is reduced. The final corona shape is supported by buoyancy and flexural stresses and will persist through geologic time. Development of lower, flatter central bowls and narrower and more pronounced annular rims and moats enhanced by thicker crusts, higher thermal gradients, and crustal thinning over the diapir.

Influence of Fault-Controlled Topography on Fluvio-Deltaic Sedimentary Systems in Eberswalde Crater, Mars

NASA Technical Reports Server (NTRS)

Rice, Melissa S.; Gupta, Sanjeev; Bell, James F., III; Warner, Nicholas H.

2011-01-01

Eberswalde crater was selected as a candidate landing site for the Mars Science Laboratory (MSL) mission based on the presence of a fan-shaped sedimentary deposit interpreted as a delta. We have identified and mapped five other candidate fluvio -deltaic systems in the crater, using images and digital terrain models (DTMs) derived from the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX). All of these systems consist of the same three stratigraphic units: (1) an upper layered unit, conformable with (2) a subpolygonally fractured unit, unconformably overlying (3) a pitted unit. We have also mapped a system of NNE-trending scarps interpreted as dip-slip faults that pre-date the fluvial -lacustrine deposits. The post-impact regional faulting may have generated the large-scale topography within the crater, which consists of a Western Basin, an Eastern Basin, and a central high. This topography subsequently provided depositional sinks for sediment entering the crater and controlled the geomorphic pattern of delta development.

The global topography of Mars and implications for surface evolution

NASA Technical Reports Server (NTRS)

Smith, D. E.; Zuber, M. T.; Solomon, S. C.; Phillips, R. J.; Head, J. W.; Garvin, J. B.; Banerdt, W. B.; Muhleman, D. O.; Pettengill, G. H.; Neumann, G. A.;

Effects of electropolishing surface treatment on the cyclic fatigue resistance of BioRace nickel-titanium rotary instruments.

PubMed

Lopes, Hélio P; Elias, Carlos N; Vieira, Victor T L; Moreira, Edson J L; Marques, Raquel V L; de Oliveira, Julio C Machado; Debelian, Gilberto; Siqueira, José F

2010-10-01

This study evaluated the influence of electropolishing surface treatment on the number of cycles to fracture of BioRace rotary nickel-titanium endodontic instruments. BioRace size BR5C instruments with or without electropolishing surface treatment were used in an artificial curved canal under rotational speed of 300 rpm until fracture. Fractured surfaces and the helical shafts of fractured instruments were analyzed by scanning electron microscopy (SEM). Polished instruments displayed a significantly higher number of cycles to fracture when compared with nonpolished instruments (P < .001). Actually, the number of cycles to fracture of a polished BR5C instrument was 124% higher than that of a nonpolished instrument. SEM analysis showed that the fractured surface of both polished and nonpolished BR5C instruments had ductile morphologic characteristics. Evaluation of the separated fragments after cyclic fatigue testing showed the presence of microcracks near the fracture surface. Polished instruments exhibited fine cracks that assumed an irregular path (zigzag crack pattern), whereas nonpolished instruments showed cracks running along the machining grooves. Electropolishing surface treatment of BioRace endodontic instruments significantly increased the cyclic fatigue resistance. Copyright © 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Evolutionary computation applied to the reconstruction of 3-D surface topography in the SEM.

PubMed

Kodama, Tetsuji; Li, Xiaoyuan; Nakahira, Kenji; Ito, Dai

2005-10-01

A genetic algorithm has been applied to the line profile reconstruction from the signals of the standard secondary electron (SE) and/or backscattered electron detectors in a scanning electron microscope. This method solves the topographical surface reconstruction problem as one of combinatorial optimization. To extend this optimization approach for three-dimensional (3-D) surface topography, this paper considers the use of a string coding where a 3-D surface topography is represented by a set of coordinates of vertices. We introduce the Delaunay triangulation, which attains the minimum roughness for any set of height data to capture the fundamental features of the surface being probed by an electron beam. With this coding, the strings are processed with a class of hybrid optimization algorithms that combine genetic algorithms and simulated annealing algorithms. Experimental results on SE images are presented.

Understanding how surface chemistry and topography enhance fog harvesting based on the superwetting surface with patterned hemispherical bulges.

PubMed

Zhong, Lieshuang; Zhu, Hai; Wu, Yang; Guo, Zhiguang

2018-09-01

The Namib Desert beetle-Stenocara can adapt to the arid environment by its fog harvesting ability. A series of samples with different topography and wettability that mimicked the elytra of the beetle were fabricated to study the effect of these factors on fog harvesting. The superhydrophobic bulgy sample harvested 1.5 times the amount of water than the sample with combinational pattern of hydrophilic bulgy/superhydrophobic surrounding and 2.83 times than the superhydrophobic surface without bulge. These bulges focused the droplets around them which endowed droplets with higher velocity and induced the highest dynamic pressure atop them. Superhydrophobicity was beneficial for the departure of harvested water on the surface of sample. The bulgy topography, together with surface wettability, dominated the process of water supply and water removal. Copyright © 2018 Elsevier Inc. All rights reserved.

Correlation between three-dimentional surface topography and color stability of different nanofilled composites.

PubMed

Öztürk, Elif; Güder, Gizem

2015-01-01

The aim of this study was to evaluate the 3-dimensional (3D) surface topography and color stability of four different resin composites after immersion in different soft-beverages. One hundred sixty disk-shaped specimens (diameter: 10 mm, and thickness: 2 mm) were made from four different resin composites (i.e., Filtek Z550, Tetric N-Ceram, Clearfil Majesty Esthetic, and Cavex Quadrant Universal LC). Each specimen was cured under mylar strips for 20 sec for both top and bottom surfaces. All of the specimens were stored in distilled water for 24 h at 37°C. Surface measurements were carried out using a noncontact 3D-optical-profilometer in terms of surface topography (Ra values). Color measurements of each specimen were performed with Vita Easy Shade system. All the measurements were performed at baseline and after 30 days of immersion in the selected soft-beverages (Redbull, Coca-Cola and Dimes-Lemonade). Control groups were stored in distilled water during the study. Ra values and color changes (ΔE values) of the groups were recorded. The data were statistically analyzed using a one way ANOVA and Tukey's post-hoc tests (SPSS 18.0). The tested soft-beverages in the present study caused color changes at a 30-day evaluation period for the tested resin composites (p < 0.05). However, 3D surface topography of resin composites was not influenced by the tested soft-beverages (p > 0.05). There was no significant interaction between the composite and beverage type on the Ra values of the resin composites (p > 0.05). No correlation was found between color stability and 3D surface topography of the resin composites. Color stability of resin composites may be affected by soft beverages. © Wiley Periodicals, Inc.

Epidemiological profile of extremity fractures in victims of motorcycle accidents

PubMed Central

Batista, Flamarion dos Santos; Silveira, Leandro Oliveira; Castillo, Jesús José André Quintana; de Pontes, Jady Elen; Villalobos, Luz Delícia Castillo

2015-01-01

Objective: Show the epidemiological profile of limb fractures in victim of motorcycle accident seen at the Emergency Department of Hospital Universitário Evangélico de Curitiba (HUEC), Curitiba, PR, Brazil, from January 2007 to December 2013, as well as to compare the results with data from the literature. Methods: This is a retrospective, descriptive, observational study. The information was obtained from the analysis of all the medical records from January 2007 to December 2013 belonging to the hospital archives. Only extremity fractures cases from motorcycle accident victims were analyzed, according to the medical records and radiological reports. The ICD-10 was used as classification criterion, and the fractures were grouped depending on the topography of the injury. The following variables were considered: number of victims, gender, age and fracture site, in order to create a database to contrast with the literature. Results: During seven years, 3,528 motorcycle accident victims have been identified, 88.29% being male, whereas 11.71% being female. The average age of the victims was 29.7 years old, observing a strong inverse correlation between the number of victims and their ages. There has been 4,365 fractures, being 59.66% in lower limbs and 40.34% in upper limbs. From that total, 18.14% were leg fractures, 11.57% were hand fractures and 10.65% were wrist fractures. Conclusion: This study has met its objectives and the results were similar to the national literature. Level of Evidence II, Retropective Study. PMID:26327795

The Role of Interface on the Impact Characteristics and Cranial Fracture Patterns Using the Immature Porcine Head Model.

PubMed

Deland, Trevor S; Niespodziewanski, Emily; Fenton, Todd W; Haut, Roger C

2016-01-01

The role of impact interface characteristics on the biomechanics and patterns of cranial fracture has not been investigated in detail, and especially for the pediatric head. In this study, infant porcine skulls aged 2-19 days were dropped with an energy to cause fracturing onto four surfaces varying in stiffness from a rigid plate to one covered with plush carpeting. Results showed that heads dropped onto the rigid surface produced more extensive cranial fracturing than onto carpeted surfaces. Contact forces generated at fracture initiation and the overall maximum contact forces were generally lower for the rigid than carpeted impacts. While the degree of cranial fracturing from impacts onto the heavy carpeted surface was comparable to that of lower-energy rigid surface impacts, there were fewer diastatic fractures. This suggests that characteristics of the cranial fracture patterns may be used to differentiate energy level from impact interface in pediatric forensic cases. © 2015 American Academy of Forensic Sciences.

Measurements of radiated elastic wave energy from dynamic tensile cracks

NASA Technical Reports Server (NTRS)

Boler, Frances M.

1990-01-01

The role of fracture-velocity, microstructure, and fracture-energy barriers in elastic wave radiation during a dynamic fracture was investigated in experiments in which dynamic tensile cracks of two fracture cofigurations of double cantilever beam geometry were propagating in glass samples. The first, referred to as primary fracture, consisted of fractures of intact glass specimens; the second configuration, referred to as secondary fracture, consisted of a refracture of primary fracture specimens which were rebonded with an intermittent pattern of adhesive to produce variations in fracture surface energy along the crack path. For primary fracture cases, measurable elastic waves were generated in 31 percent of the 16 fracture events observed; the condition for radiation of measurable waves appears to be a local abrupt change in the fracture path direction, such as occurs when the fracture intersects a surface flaw. For secondary fractures, 100 percent of events showed measurable elastic waves; in these fractures, the ratio of radiated elastic wave energy in the measured component to fracture surface energy was 10 times greater than for primary fracture.

In vitro study on bone formation and surface topography from the standpoint of biomechanics.

PubMed

Kawahara, H; Soeda, Y; Niwa, K; Takahashi, M; Kawahara, D; Araki, N

2004-12-01

Effect of surface topography upon cell-adhesion, -orientation and -differentiation was investigated by in vitro study on cellular responses to titanium substratum with different surface roughness. Cell-shape, -function and -differentiation depending upon the surface topography were clarified by use of bone formative group cells (BFGCs) derived from bone marrow of beagle's femur. BFGCs consisted of hematopoietic stem cells (HSC) and osteogenetic stem cells (OSC). Cell differentiation of BFGCs was expressed and promoted by structural changes of cytoskeleton, and cell-organella, which was caused by mechanical stress with cytoplasmic stretching of cell adhesions to the substratum. Phagocytic monocytes of HSC differentiated to osteomediator cells (OMC) by cytoplasmic stretching with cell adhesion to the substratum. The OMC mediated and promoted cell differentiation from OSC to osteoblast through osteoblastic phenotype cell (OBC) by cell-aggregation of nodules with "pile up" phenomenon of OBC onto OMC. The osteogenesis might be performed by coupling work of both cells, OMC originated from monocyte of HSC and OBC originated from OSC, which were explained by SEM, TEM and fluorescent probe investigation on BFGCs on the test plate of cp titanium plates with different topographies. This osteogenetic process was proved by investigating cell proliferation, DNA contents, cell-adhesion, alkaline phosphatase activity and osteocalcine productivity for cells on the titanium plates with different topographies. The study showed increased osteogenic effects for cells cultured on Ti with increased surface roughness. Possible mechanisms were discussed from a biomechanical perspective.

Effect of metal surface topography on mechanical bonding at simulated total hip stem-cement interfaces.

PubMed

Chen, C Q; Scott, W; Barker, T M

1999-01-01

Bonding and loosening mechanisms between bone cement and joint prostheses have not been well identified. In this study, the effects of simulated hip stem surface topography on the interfacial shear strength were examined. Six different surface topographies were used. They were described by several surface characterization parameters that may directly relate to the interfacial bonding strength: average surface roughness R(a), root mean square slope R(Deltaq), correlation length beta, and fluid retention index R(ri). The shear strengths between Palacos E bone cement and stainless steel rods were measured using an Instron materials testing machine. We found that cement can "flow" into the surface microtopography and establish good contact with the metal surface. The results show that the interfacial strength increases monotonically with the increase of R(Deltaq) instead of with R(a). The relationship between interfacial strength and surface parameters shows that a metal stem with an isotropic surface texture, higher R(Deltaq), and greater R(ri) gives a higher interfacial strength. Copyright 1999 John Wiley & Sons, Inc.

Surface Fractal Analysis for Estimating the Fracture Energy Absorption of Nanoparticle Reinforced Composites

PubMed Central

Pramanik, Brahmananda; Tadepalli, Tezeswi; Mantena, P. Raju

2012-01-01

In this study, the fractal dimensions of failure surfaces of vinyl ester based nanocomposites are estimated using two classical methods, Vertical Section Method (VSM) and Slit Island Method (SIM), based on the processing of 3D digital microscopic images. Self-affine fractal geometry has been observed in the experimentally obtained failure surfaces of graphite platelet reinforced nanocomposites subjected to quasi-static uniaxial tensile and low velocity punch-shear loading. Fracture energy and fracture toughness are estimated analytically from the surface fractal dimensionality. Sensitivity studies show an exponential dependency of fracture energy and fracture toughness on the fractal dimensionality. Contribution of fracture energy to the total energy absorption of these nanoparticle reinforced composites is demonstrated. For the graphite platelet reinforced nanocomposites investigated, surface fractal analysis has depicted the probable ductile or brittle fracture propagation mechanism, depending upon the rate of loading. PMID:28817017

Surface finish measurement studies

NASA Technical Reports Server (NTRS)

Teague, E. C.

1983-01-01

The performance of stylus instruments for measuring the topography of National Transonic Facility (NTF) model surfaces both for monitoring during fabrication and as an absolute measurement of topography was evaluated. It was found that the shop-grade instruments can damage the surface of models and that their use for monitoring fabrication procedures can lead to surface finishes that are substantially out of range in critical areas of the leading edges. The development of a prototype light-scattering instrument which would allow for rapid assessment of the surface finish of a model is also discussed.

Topographic forcing and related uncertainties on glacier surface energy balance in High Mountain Asia

NASA Astrophysics Data System (ADS)

Olson, M.; Rupper, S.; Shean, D. E.

2017-12-01

Topography directly influences the amount of global radiation, as well as other key energy flux terms, arriving on a glacier surface. This is particularly important in regions of variable and complex topography such as High Mountain Asia (HMA). In this region surface energy and mass balance estimates often rely heavily on modeling, and thus require accurate accounting of topography through available remote sensing platforms. Our previous work shows that topographic shading from surrounding terrain can alter the mean daily potential direct shortwave radiation by upwards of 20% for some valley glaciers. In this work, we find in regions of high topographic relief that shading frequently dominates in the ablation zone rather than the accumulation zone, contrary to the findings of some previous studies. This however, is largely dependent on the valley aspect and relative relief of nearby terrain. In addition, we examine the impact of topography, primarily topographic shading, on components of surface energy balance for a large sample of glaciers across different regions in HMA. Our results show that while the impact of topographic shading is highly variable throughout HMA, the magnitude of influence can often be predicted based on simple characteristics such as latitude, valley aspect, and orientation of the immediate surrounding topography. We also explore the uncertainty in topographic shading and in calculated surface energy due to the spatial resolution and accuracy of DEMs. In particular, we compare the shading and energy balance results utilizing a suite of DEMs, including 2 m, 8 m, and 30 m World View DEMs, 30 m ASTER GDEM, 30 m SRTM DEM, and 30 m ALOS DEM. These results will help us improve glacier energy and mass balance modeling accuracy, and demonstrate limitations and uncertainties when modeling changes in surface energy fluxes due to surrounding topography for mountain glaciers.

Engineered microtopographies and surface chemistries direct cell attachment and function

NASA Astrophysics Data System (ADS)

Magin, Chelsea Marie

Harrison, in 1914, first recognized that cells respond to physicochemical cues such as substratum topography when he observed that fibroblasts elongated while cultured on spider silk. Recently, techniques developed in the micro-electronics industry have been used to create molds for producing microscaled topographies with various shapes and spatial arrangements. Although these patterning techniques are well-established, very little is known about the mechanisms underlying cell sensing and response to microtopographies. In this work cellular micro-environments with varying surface topographies and chemistries were evaluated with marine organisms and mammalian cells to investigate cellular sensing and response. Biofouling---the accumulation of micro-organisms, plants, and animals on submerged surfaces---is an environmental and economic concern. Engineered topographies, replicated in polydimethylsiloxane elastomer (PDMSe) and functionalized poly(ethylene glycol)-dimethacrylate (PEGDMA) hydrogels, were evaluated for inhibition of marine fouling organism attachment. Microtopographies replicated in PDMSe inhibited attachment of the marine bacterium, Cobetia marina up to 99% versus smooth. The average normalized attachment densities of cells of C. marina and zoospores of the green algae Ulva on PDMSe topographies scaled inversely with the Engineered Roughness Index (ERIII), a representation of surface energy. Attachment densities of Ulva from four assays and C. marina from two growth phases to PDMSe surfaces scaled inversely with one equation: ERI II multiplied by the Reynolds number of the organism (Re) (R 2 = 0.77). The same microtopographies created in PDMSe reduced the initial attachment density and attachment strength of cells of the diatoms Navicula incerta and Seminavis robusta compared to smooth PDMSe. The average normalized attachment density of Navicula after exposure to shear stress (48 Pa) was correlated with the contact area between the diatom and a topographically modified surface (R2=0.82). Functionalized PEGDMA hydrogels significantly reduced attachment and attachment strength of Navicula and C. marina. These hydrogels also reduced attachment of zoospores of Ulva compared to PDMSe. Attachment of Ulva to microtopographies in PDMSe and PEGDMA-co-HEMA negatively correlated with ERIII*Re (R2 = 0.94 and R2 = 0.99, respectively). Incorporating a surface energy term into this equation created a correlation between the attachment densities of cells from two evolutionarily diverse groups on substrates of two surface chemistries with an equation that describes the various microtopographies and surface chemistries in terms of surface energy (R2 = 0.80). The current Attachment Model can now be used to design engineered antifouling surface microtopographies and chemistries that inhibit the attachment of organisms from three evoluntionarily diverse groups. Hydrogels based on PEGDMA were also chosen as a substratum material for mammalian cell culture. Capturing endothelial progenitor cells (EPCs) and inducing differentiation into the endothelial cell (EC) phenotype is the ideal way to re-endothelialize a small-diameter vascular graft. Substratum elasticity has been reported to direct stem cell differentiation into specific lineages. Functionalized PEGDMA hydrogels provided good compliance, high fidelity of topographic features and sites for surface modification with biomolecules. Fibronectin grafting and topography both increased EC attachment. This combination of adjustable elasticity, surface chemistry and topography has the potential to promote the capture and differentiation of EPCs into a confluent EC monolayer. Engineered microtopographies replicated in PDMSe directed elongation and alignment of human coronary artery endothelial cells (HCAECs) and human coronary artery smooth muscle cells (HCASMCs) compared to smooth surfaces. Engineered cellular micro-environments were created with specific surface energies defined by chemistry and topography to successfully direct cell attachment and function.

Modeling the Effects of Sea-Level Rise on Groundwater Levels in Coastal New Hampshire

NASA Astrophysics Data System (ADS)

Jacobs, J. M.; Knott, J. F.; Daniel, J.; Kirshen, P. H.

2017-12-01

Coastal communities with high population density and low topography are vulnerable from sea-level rise (SLR) caused by climate change. Groundwater in coastal communities will rise with sea level impacting water quality, the structural integrity of infrastructure, and natural ecosystem health. SLR-induced groundwater rise has been studied in areas of high aquifer transmissivity and in low-lying areas immediately along the coast. In this regional study, we investigate SLR-induced groundwater rise in a coastal area characterized by shallow unconsolidated deposits overlying fractured bedrock, typical of the glaciated northeast United States. MODFLOW, a numerical groundwater-flow model, is used with groundwater observations, lidar topography, surface-water hydrology, and groundwater withdrawals to investigate SLR-induced changes in groundwater levels and vadose-zone thickness in New Hampshire's Seacoast. The SLR groundwater signal is detected up to 5 km from the coast, more than 3 times farther inland than projected surface-water flooding associated with SLR. Relative groundwater rise ranges from 38 to 98% of SLR within 1 km of the shoreline and drops below 4% between 4 and 5 km from the coast. The largest magnitude of SLR-induced groundwater rise occurs in the marine and estuarine deposits and land areas with tidal water bodies on three sides. In contrast, groundwater rise is dampened near streams. Groundwater inundation caused by 2 m of SLR is projected to contribute 48% of the total land inundation area in the City of Portsmouth with consequences for built and natural resources. Freshwater wetlands are projected to expand 3% by year 2030 increasing to 25% by year 2100 coupled with water-depth increases. These results imply that underground infrastructure and natural resources in coastal communities will be impacted by rising groundwater much farther inland than previously thought when considering only surface-water flooding from SLR.

Modeling Thermal Transport and Surface Deformation on Europa using Realistic Rheologies

NASA Astrophysics Data System (ADS)

Linneman, D.; Lavier, L.; Becker, T. W.; Soderlund, K. M.

2017-12-01

Most existing studies of Europa's icy shell model the ice as a Maxwell visco-elastic solid or viscous fluid. However, these approaches do not allow for modeling of localized deformation of the brittle part of the ice shell, which is important for understanding the satellite's evolution and unique geology. Here, we model the shell as a visco-elasto-plastic material, with a brittle Mohr-Coulomb elasto-plastic layer on top of a convective Maxwell viscoelastic layer, to investigate how thermal transport processes relate to the observed deformation and topography on Europa's surface. We use Fast Lagrangian Analysis of Continua (FLAC) code, which employs an explicit time-stepping algorithm to simulate deformation processes in Europa's icy shell. Heat transfer drives surface deformation within the icy shell through convection and tidal dissipation due to its elliptical orbit around Jupiter. We first analyze the visco-elastic behavior of a convecting ice layer and the parameters that govern this behavior. The regime of deformation depends on the magnitude of the stress (diffusion creep at low stresses, grain-size-sensitive creep at intermediate stresses, dislocation creep at high stresses), so we calculate effective viscosity each time step using the constitutive stress-strain equation and a combined flow law that accounts for all types of deformation. Tidal dissipation rate is calculated as a function of the temperature-dependent Maxwell relaxation time and the square of the second invariant of the strain rate averaged over each orbital period. After we initiate convection in the viscoelastic layer by instituting an initial temperature perturbation, we then add an elastoplastic layer on top of the convecting layer and analyze how the brittle ice reacts to stresses from below and any resulting topography. We also take into account shear heating along fractures in the brittle layer. We vary factors such as total shell thickness and minimum viscosity, as these parameters are not well constrained, and determine how this affects the thickness and deformation of the brittle layer.

Surface topography and roughness of high-speed milled AlMn1Cu

NASA Astrophysics Data System (ADS)

Wang, Zhenhua; Yuan, Juntang; Yin, Zengbin; Hu, Xiaoqiu

2016-10-01

The aluminum alloy AlMn1Cu has been broadly applied for functional parts production because of its good properties. But few researches about the machining mechanism and the surface roughness were reported. The high-speed milling experiments are carried out in order to improve the machining quality and reveal the machining mechanism. The typical topography features of machined surface are observed by scan electron microscope(SEM). The results show that the milled surface topography is mainly characterized by the plastic shearing deformation surface and material piling zone. The material flows plastically along the end cutting edge of the flat-end milling tool and meanwhile is extruded by the end cutting edge, resulting in that materials partly adhere to the machined surface and form the material piling zone. As the depth of cut and the feed per tooth increase, the plastic flow of materials is strengthened and the machined surface becomes rougher. However, as the cutting speed increases, the plastic flow of materials is weakened and the milled surface becomes smoother. The cutting parameters (e.g. cutting speed, feed per tooth and depth of cut) influencing the surface roughness are analyzed. It can be concluded that the roughness of the machined surface formed by the end cutting edge is less than that by the cylindrical cutting edge when a cylindrical flat-end mill tool is used for milling. The proposed research provides the typical topography features of machined surface of the anti-rust aluminum alloy AlMn1Cu in high speed milling.

Topographic modelling of haptic properties of tissue products

NASA Astrophysics Data System (ADS)

Rosen, B.-G.; Fall, A.; Rosen, S.; Farbrot, A.; Bergström, P.

2014-03-01

The way a product or material feels when touched, haptics, has been shown to be a property that plays an important role when consumers determine the quality of products For tissue products in constant touch with the skin, softness" becomes a primary quality parameter. In the present work, the relationship between topography and the feeling of the surface has been investigated for commercial tissues with varying degree of texture from the low textured crepe tissue to the highly textured embossed- and air-dried tissue products. A trained sensory panel at was used to grade perceived haptic "roughness". The technique used to characterize the topography was Digital light projection (DLP) technique, By the use of multivariate statistics, strong correlations between perceived roughness and topography were found with predictability of above 90 percent even though highly textured products were included. Characterization was made using areal ISO 25178-2 topography parameters in combination with non-contacting topography measurement. The best prediction ability was obtained when combining haptic properties with the topography parameters auto-correlation length (Sal), peak material volume (Vmp), core roughness depth (Sk) and the maximum height of the surface (Sz).

The impact of runoff and surface hydrology on Titan's climate

NASA Astrophysics Data System (ADS)

Faulk, Sean; Lora, Juan; Mitchell, Jonathan

2017-10-01

Titan’s surface liquid distribution has been shown by general circulation models (GCMs) to greatly influence the hydrological cycle. Simulations from the Titan Atmospheric Model (TAM) with imposed polar methane “wetlands” reservoirs realistically produce many observed features of Titan’s atmosphere, whereas “aquaplanet” simulations with a global methane ocean are not as successful. In addition, wetlands simulations, unlike aquaplanet simulations, demonstrate strong correlations between extreme rainfall behavior and observed geomorphic features, indicating the influential role of precipitation in shaping Titan’s surface. The wetlands configuration is, in part, motivated by Titan’s large-scale topography featuring low-latitude highlands and high-latitude lowlands, with the implication being that methane may concentrate in the high-latitude lowlands by way of runoff and subsurface flow. However, the extent to which topography controls the surface liquid distribution and thus impacts the global hydrological cycle by driving surface and subsurface flow is unclear. Here we present TAM simulations wherein the imposed wetlands reservoirs are replaced by a surface runoff scheme that allows surface liquid to self-consistently redistribute under the influence of topography. To isolate the singular impact of surface runoff on Titan’s climatology, we run simulations without parameterizations of subsurface flow and topography-atmosphere interactions. We discuss the impact of surface runoff on the surface liquid distribution over seasonal timescales and compare the resulting hydrological cycle to observed cloud and surface features, as well as to the hydrological cycles of the TAM wetlands and aquaplanet simulations. While still idealized, this more realistic representation of Titan’s hydrology provides new insight into the complex interaction between Titan’s atmosphere and surface, demonstrates the influence of surface runoff on Titan’s global climate, and lays the groundwork for further surface hydrology developments in Titan GCMs.

Hydrogeology and simulation of groundwater flow in fractured-rock aquifers of the Piedmont and Blue Ridge Physiographic Provinces, Bedford County, Virginia

USGS Publications Warehouse

McCoy, Kurt J.; White, Bradley A.; Yager, Richard M.; Harlow, George E.

2015-09-11

A steady-state groundwater-flow simulation for Bedford County was developed to test the conceptual understanding of flow in the fractured-rock aquifers and to compute a groundwater budget for the four major drainages: James River, Smith Mountain and Leesville Lakes, Goose Creek, and Big Otter River. Model results indicate that groundwater levels mimic topography and that minimal differences in aquifer properties exist between the Proterozoic basement crystalline rocks and Late Proterozoic-Cambrian cover crystalline rocks. The Big Otter River receives 40.8 percent of the total daily groundwater outflow from fractured-rock aquifers in Bedford County; Goose Creek receives 25.8 percent, the James River receives 18.2 percent, and Smith Mountain and Leesville Lakes receive 15.2 percent. The remaining percentage of outflow is attributed to pumping from the aquifer (consumptive use).

Membrane fouling in a submerged membrane bioreactor: An unified approach to construct topography and to evaluate interaction energy between two randomly rough surfaces.

PubMed

Cai, Xiang; Shen, Liguo; Zhang, Meijia; Chen, Jianrong; Hong, Huachang; Lin, Hongjun

2017-11-01

Quantitatively evaluating interaction energy between two randomly rough surfaces is the prerequisite to quantitatively understand and control membrane fouling in membrane bioreactors (MBRs). In this study, a new unified approach to construct rough topographies and to quantify interaction energy between a randomly rough particle and a randomly rough membrane was proposed. It was found that, natural rough topographies of both foulants and membrane could be well constructed by a modified two-variable Weierstrass-Mandelbrot (WM) function included in fractal theory. Spatial differential relationships between two constructed surfaces were accordingly established. Thereafter, a new approach combining these relationships, surface element integration (SEI) approach and composite Simpson's rule was deduced to calculate the interaction energy between two randomly rough surfaces in a submerged MBR. The obtained results indicate the profound effects of surface morphology on interaction energy and membrane fouling. This study provided a basic approach to investigate membrane fouling and interface behaviors. Copyright © 2017 Elsevier Ltd. All rights reserved.

The influence of open fracture anisotropy on CO2 movement within geological storage complexes

NASA Astrophysics Data System (ADS)

Bond, C. E.; Wightman, R.; Ringrose, P. S.

2012-12-01

Carbon mitigation through the geological storage of carbon dioxide is dependent on the ability of geological formations to store CO2 trapping it within a geological storage complex. Secure long-term containment needs to be demonstrated, due to both political and social drivers, meaning that this containment must be verifiable over periods of 100-105 years. The effectiveness of sub-surface geological storage systems is dependent on trapping CO2 within a volume of rock and is reliant on the integrity of the surrounding rocks, including their chemical and physical properties, to inhibit migration to the surface. Oil and gas reservoir production data, and field evidence show that fracture networks have the potential to act as focused pathways for fluid movement. Fracture networks can allow large volumes of fluid to migrate to the surface within the time scales of interest. In this paper we demonstrate the importance of predicting the effects of fracture networks in storage, using a case study from the In Salah CO2 storage site, and show how the fracture permeability is closely controlled by the stress regime that determines the open fracture network. Our workflow combines well data of imaged fractures, with a discrete fracture network (DFN) model of tectonically induced fractures, within the horizon of interest. The modelled and observed fractures have been compared and combined with present day stress data to predict the open fracture network and its implications for anisotropic movement of CO2 in the sub-surface. The created fracture network model has been used to calculate the 2D permeability tensor for the reservoir for two scenarios: 1) a model in which all fractures are permeable, based on the whole DFN model and 2) those fractures determined to be in dilatational failure under the present day stress regime, a sub-set of the DFN. The resulting permeability anisotropy tensors show distinct anisotropies for the predicted CO2 movement within the reservoir. These predictions have been compared with InSAR imagery of surface uplift, used as an indicator of fluid pressure and movement in the sub-surface, around the CO2 injection wells. The analysis shows that the permeability tensor with the greatest anisotropy, that for the DFN sub-set of open fractures, matches well with the anisotropy in surface uplift imaged by InSAR. We demonstrate that predicting fracture networks alone does not predict fluid movement in the sub-surface, and that fracture permeability is closely controlled by the stress regime that determines the open fracture network. Our results show that a workflow of fracture network prediction combined with present day stress analysis can be used to successfully predict CO2 movement in the sub-surface at an active injection site.

Quantifying the pattern of microbial cell dispersion, density and clustering on surfaces of differing chemistries and topographies using multifractal analysis.

PubMed

Wickens, David; Lynch, Stephen; West, Glen; Kelly, Peter; Verran, Joanna; Whitehead, Kathryn A

2014-09-01

The effects of surface topography on bacterial distribution across a surface are of extreme importance when designing novel, hygienic or antimicrobial surface coatings. The majority of methods that are deployed to describe the pattern of cell dispersion, density and clustering across surfaces are currently qualitative. This paper presents a novel application of multifractal analysis to quantitatively measure these factors using medically relevant microorganisms (Staphylococcus aureus or Staphylococcus epidermidis). Surfaces (medical grade 316 stainless steel) and coatings (Ti-ZrN, Ti-ZrN/6.0%Ag, Ti-ZrN/15.6%Ag, TiZrN/24.7%Ag) were used in microbiological retention assays. Results demonstrated that S. aureus displayed a more heterogeneous cell dispersion (∆αAS<1) whilst the dispersion of S. epidermidis was more symmetric and homogeneous (∆αAS≥1). Further, although the surface topography and chemistry had an effect on cell dispersion, density and clustering, the type of bonding that occurred at the surface interface was also important. Both types of cells were influenced by both surface topographical and chemical effects; however, S. aureus was influenced marginally more by surface chemistry whilst S. epidermidis cells was influenced marginally more by surface topography. Thus, this effect was bacterially species specific. The results demonstrate that multifractal analysis is a method that can be used to quantitatively analyse the cell dispersion, density and clustering of retained microorganisms on surfaces. Using quantitative descriptors has the potential to aid the understanding the effect of surface properties on the production of hygienic and antimicrobial coatings. Copyright © 2014 Elsevier B.V. All rights reserved.

Three-channel false colour AFM images for improved interpretation of complex surfaces: a study of filamentous cyanobacteria.

PubMed

Kurk, Toby; Adams, David G; Connell, Simon D; Thomson, Neil H

2010-05-01

Imaging signals derived from the atomic force microscope (AFM) are typically presented as separate adjacent images with greyscale or pseudo-colour palettes. We propose that information-rich false-colour composites are a useful means of presenting three-channel AFM image data. This method can aid the interpretation of complex surfaces and facilitate the perception of information that is convoluted across data channels. We illustrate this approach with images of filamentous cyanobacteria imaged in air and under aqueous buffer, using both deflection-modulation (contact) mode and amplitude-modulation (tapping) mode. Topography-dependent contrast in the error and tertiary signals aids the interpretation of the topography signal by contributing additional data, resulting in a more detailed image, and by showing variations in the probe-surface interaction. Moreover, topography-independent contrast and topography-dependent contrast in the tertiary data image (phase or friction) can be distinguished more easily as a consequence of the three dimensional colour-space.

Facile Synthesis of Conductive Polypyrrole Wrinkle Topographies on Polydimethylsiloxane via a Swelling-Deswelling Process and Their Potential Uses in Tissue Engineering.

PubMed

Aufan, M Rifqi; Sumi, Yang; Kim, Semin; Lee, Jae Young

2015-10-28

Electrically conducting biomaterials have gained great attention in various biomedical studies especially to influence cell and tissue responses. In addition, wrinkling can present a unique topography that can modulate cell-material interactions. In this study, we developed a simple method to create wrinkle topographies of conductive polypyrrole (wPPy) on soft polydimethylsiloxane surfaces via a swelling-deswelling process during and after PPy polymerization and by varying the thickness of the PPy top layers. As a result, various features of wPPy in the range of the nano- and microscales were successfully obtained. In vitro cell culture studies with NIH 3T3 fibroblasts and PC12 neuronal cells indicated that the conductive wrinkle topographies promote cell adhesion and neurite outgrowth of PC12 cells. Our studies help to elucidate the design of the surface coating and patterning of conducting polymers, which will enable us to simultaneously provide topographical and electrical signals to improve cell-surface interactions for potential tissue-engineering applications.

Anomalous topography on the continental shelf around Hudson Canyon

USGS Publications Warehouse

Knebel, H.J.

1979-01-01

Recent seismic-reflection data show that the topography on the Continental Shelf around Hudson Canyon is composed of a series of depressions having variable spacings (< 100 m to 2 km), depths (1-10 m), outlines, and bottom configurations that give the sea floor an anomalous "jagged" appearance in profile. The acoustic and sedimentary characteristics, the proximity to relict shores, and the areal distribution indicate that this rough topography is an erosional surface formed on Upper Pleistocene silty sands about 13,000 to 15,000 years ago by processes related to Hudson Canyon. The pronounced southward extension of the surface, in particular, may reflect a former increase in the longshore-current erosion capacity caused by the loss of sediments over the canyon. Modern erosion or nondeposition of sediments has prevented the ubiquitous sand sheet on the Middle Atlantic shelf from covering the surface. The "anomalous" topography may, in fact, be characteristic of areas near other submarine canyons that interrupt or have interrupted the longshore drift of sediments. ?? 1979.

Photometric stereo endoscopy

PubMed Central

Parot, Vicente; Lim, Daryl; González, Germán; Traverso, Giovanni; Nishioka, Norman S.; Vakoc, Benjamin J.

2013-01-01

Abstract. While color video endoscopy has enabled wide-field examination of the gastrointestinal tract, it often misses or incorrectly classifies lesions. Many of these missed lesions exhibit characteristic three-dimensional surface topographies. An endoscopic system that adds topographical measurements to conventional color imagery could therefore increase lesion detection and improve classification accuracy. We introduce photometric stereo endoscopy (PSE), a technique which allows high spatial frequency components of surface topography to be acquired simultaneously with conventional two-dimensional color imagery. We implement this technique in an endoscopic form factor and demonstrate that it can acquire the topography of small features with complex geometries and heterogeneous optical properties. PSE imaging of ex vivo human gastrointestinal tissue shows that surface topography measurements enable differentiation of abnormal shapes from surrounding normal tissue. Together, these results confirm that the topographical measurements can be obtained with relatively simple hardware in an endoscopic form factor, and suggest the potential of PSE to improve lesion detection and classification in gastrointestinal imaging. PMID:23864015

Noise evaluation of a point autofocus surface topography measuring instrument

NASA Astrophysics Data System (ADS)

Maculotti, Giacomo; Feng, Xiaobing; Galetto, Maurizio; Leach, Richard

2018-06-01

In this work, the measurement noise of a point autofocus surface topography measuring instrument is evaluated, as the first step towards establishing a route to traceability for this type of instrument. The evaluation is based on the determination of the metrological characteristics for noise as outlined in draft ISO specification standards by using a calibrated optical flat. The static noise and repeatability of the autofocus sensor are evaluated. The influence of environmental disturbances on the measured surface topography and the built-in software to compensate for such influences are also investigated. The instrument was found to have a measurement noise of approximately 2 nm or, when expressed with the measurement bandwidth, 0.4 nm for a single-point measurement.

A method for surface topography measurement using a new focus function based on dual-tree complex wavelet transform

NASA Astrophysics Data System (ADS)

Li, Shimiao; Guo, Tong; Yuan, Lin; Chen, Jinping

2018-01-01

Surface topography measurement is an important tool widely used in many fields to determine the characteristics and functionality of a part or material. Among existing methods for this purpose, the focus variation method has proved high performance particularly in large slope scenarios. However, its performance depends largely on the effectiveness of focus function. This paper presents a method for surface topography measurement using a new focus measurement function based on dual-tree complex wavelet transform. Experiments are conducted on simulated defocused images to prove its high performance in comparison with other traditional approaches. The results showed that the new algorithm has better unimodality and sharpness. The method was also verified by measuring a MEMS micro resonator structure.

Experiments on topographies lacking tidal conversion

NASA Astrophysics Data System (ADS)

Maas, Leo; Paci, Alexandre; Yuan, Bing

2015-11-01

In a stratified sea, internal tides are supposedly generated when the tide passes over irregular topography. It has been shown that for any given frequency in the internal wave band there are an infinite number of exceptions to this rule of thumb. This ``stealth-like'' property of the topography is due to a subtle annihilation of the internal waves generated during the surface tide's passage over the irregular bottom. We here demonstrate this in a lab-experiment. However, for any such topography, subsequently changing the surface tide's frequency does lead to tidal conversion. The upshot of this is that a tidal wave passing over an irregular bottom is for a substantial part trapped to this irregularity, and only partly converted into freely propagating internal tides. Financially supported by the European Community's 7th Framework Programme HYDRALAB IV.

Titania-polymeric powder coatings with nano-topography support enhanced human mesenchymal cell responses.

PubMed

Mozumder, Mohammad Sayem; Zhu, Jesse; Perinpanayagam, Hiran

2012-10-01

Titanium implant osseointegration is dependent on the cellular response to surface modifications and coatings. Titania-enriched nanocomposite polymeric resin coatings were prepared through the application of advanced ultrafine powder coating technology. Their surfaces were readily modified to create nano-rough (<100 nm) surface nano-topographies that supported human embryonic palatal mesenchymal cell responses. Energy dispersive x-ray spectroscopy confirmed continuous and homogenous coatings with a similar composition and even distribution of titanium. Scanning electron microscopy (SEM) showed complex micro-topographies, and atomic force microscopy revealed intricate nanofeatures and surface roughness. Cell counts, mitochondrial enzyme activity reduction of yellow 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to dark purple, SEM, and inverted fluorescence microscopy showed a marked increase in cell attachment, spreading, proliferation, and metabolic activity on the nanostructured surfaces. Reverse Transcription- Polymerase Chain Reaction (RT-PCR) analysis showed that type I collagen and Runx2 expression were induced, and Alizarin red staining showed that mineral deposits were abundant in the cell cultures grown on nanosurfaces. This enhancement in human mesenchymal cell attachment, growth, and osteogenesis were attributed to the nanosized surface topographies, roughness, and moderate wetting characteristics of the coatings. Their dimensional similarity to naturally occurring matrix proteins and crystals, coupled with their increased surface area for protein adsorption, may have facilitated the response. Therefore, this application of ultrafine powder coating technology affords highly biocompatible surfaces that can be readily modified to accentuate the cellular response. Copyright © 2012 Wiley Periodicals, Inc.

Source Physics Experiment: Research in Support of Verification and Nonproliferation

DTIC Science & Technology

2011-09-01

designed to provide a carefully controlled seismic and strong motion data set from buried explosions at the Nevada National Security Site (NNSS). The...deposition partitioned into internal (heat and plastic strain) and kinetic (e.g., radiated seismic ) energy, giving more confidence in predicted free...ample information to study dry and water-saturated fractures, local lithology and topography on the radiated seismic wavefield. Spallation on

Open questions in surface topography measurement: a roadmap

NASA Astrophysics Data System (ADS)

Leach, Richard; Evans, Christopher; He, Liangyu; Davies, Angela; Duparré, Angela; Henning, Andrew; Jones, Christopher W.; O'Connor, Daniel

2015-03-01

Control of surface topography has always been of vital importance for manufacturing and many other engineering and scientific disciplines. However, despite over one hundred years of quantitative surface topography measurement, there are still many open questions. At the top of the list of questions is ‘Are we getting the right answer?’ This begs the obvious question ‘How would we know?’ There are many other questions relating to applications, the appropriateness of a technique for a given scenario, or the relationship between a particular analysis and the function of the surface. In this first ‘open questions’ article we have gathered together some experts in surface topography measurement and asked them to address timely, unresolved questions about the subject. We hope that their responses will go some way to answer these questions, address areas where further research is required, and look at the future of the subject. The first section ‘Spatial content characterization for precision surfaces’ addresses the need to characterise the spatial content of precision surfaces. Whilst we have been manufacturing optics for centuries, there still isn’t a consensus on how to specify the surface for manufacture. The most common three methods for spatial characterisation are reviewed and compared, and the need for further work on quantifying measurement uncertainties is highlighted. The article is focussed on optical surfaces, but the ideas are more pervasive. Different communities refer to ‘figure, mid-spatial frequencies, and finish’ and ‘form, waviness, and roughness’, but the mathematics are identical. The second section ‘Light scattering methods’ is focussed on light scattering techniques; an important topic with in-line metrology becoming essential in many manufacturing scenarios. The potential of scattering methods has long been recognized; in the ‘smooth surface limit’ functionally significant relationships can be derived from first principles for statistically stationary, random surfaces. For rougher surfaces, correlations can be found experimentally for specific manufacturing processes. Improvements in computational methods encourage us to revisit light scattering as a powerful and versatile tool to investigate surface and thin film topographies, potentially providing information on both topography and defects over large areas at high speed. Future scattering techniques will be applied for complex film systems and for sub-surface damage measurement, but more research is required to quantify and standardise such measurements. A fundamental limitation of all topography measurement systems is their finite spatial bandwidth, which limits the slopes that they can detect. The third section ‘Optical measurements of surfaces containing high slope angles’ discusses this limitation and potential methods to overcome it. In some cases, a rough surface can allow measurement of slopes outside the classical optics limit, but more research is needed to fully understand this process. The last section ‘What are the challenges for high dynamic range surface measurement?’ presents the challenge facing metrologists by the use of surfaces that need measurement systems with very high spatial and temporal bandwidths, for example, those found in roll-to-roll manufacturing. High resolution, large areas and fast measurement times are needed, and these needs are unlikely to be fulfilled by developing a single all-purpose instrument. A toolbox of techniques needs to be developed which can be applied for any specific manufacturing scenario. The functional significance of surface topography has been known for centuries. Mirrors are smooth. Sliding behaviour depends on roughness. We have been measuring surfaces for centuries, but we still face many challenges. New manufacturing paradigms suggest that we need to make rapid measurements online that relate to the functional performance of the surface. This first ‘open questions’ collection addresses a subset of the challenges facing the surface metrology community. There are many more challenges which we would like to address in future ‘open questions’ articles. We welcome your feedback and your suggestions.

Geoid, topography, and convection-driven crustal deformation on Venus

NASA Technical Reports Server (NTRS)

Simons, Mark; Hager, Bradford H.; Solomon, Sean C.

1992-01-01

High-resolution Magellan images and altimetry of Venus reveal a wide range of styles and scales of surface deformation that cannot readily be explained within the classical terrestrial plate tectonic paradigm. The high correlation of long-wavelength topography and gravity and the large apparent depths of compensation suggest that Venus lacks an upper-mantle low-viscosity zone. A key difference between Earth and Venus may be the degree of coupling between the convecting mantle and the overlying lithosphere. Mantle flow should then have recognizable signatures in the relationships between surface topography, crustal deformation, and the observed gravity field.

Relation between the fracture laws and the fatigue life of a surface-hardened pseudo-α titanium alloy

NASA Astrophysics Data System (ADS)

Bagmutov, V. P.; Vodop'yanov, V. I.; Zakharov, I. N.; Denisevich, D. S.

2016-07-01

The laws of fracture and fatigue life of the PT-3V pseudo-α titanium alloy subjected to surface hardening using electromechanical, ultrasonic, and combined treatment are studied. Fracture mechanisms and the structures of crack nucleation and growth zones are described using the results of metallographic and fractographic analysis of samples after fatigue tests. It is shown that the existence of a thin hardened layer on the sample surface changes the crack nucleation time and the state of fracture surface in the crack nucleation zone. This surface is characterized by signs of brittle or ductile fracture, which substantially affects the fatigue life of the sample.

The fracture strength of ceramic brackets: a comparative study.

PubMed

Flores, D A; Caruso, J M; Scott, G E; Jeiroudi, M T

1990-01-01

Recent demand for esthetic brackets has led to the development and use of ceramic brackets in orthodontics. The purpose of this study was to compare the fracture strength of different ceramic brackets under different surface conditions and ligation methods using a torsional wire bending force. Five different bracket types (two polycrystalline, two single-crystal, and one metal) were tested using elastic and wire ligation, with half being scratched and the other half remaining unscratched. Results showed a significant difference between bracket types and surface conditions. Non-scratched single-crystal brackets had higher fracture strengths and slightly higher fracture loads than polycrystalline brackets. However, single-crystal brackets were significantly adversely affected by surface damage (scratching), while polycrystalline brackets were not significantly affected by surface damage. The fracture behavior of ceramic brackets followed the Griffith model where fracture strength decreased following surface damage.

Ground-based LiDAR Measurements of Actively Inflating Pahoehoe Flows, Kilauea Volcano, Hawaii: Implications for Emplacement of Basaltic Units on Mars

NASA Astrophysics Data System (ADS)

Byrnes, J. M.; Finnegan, D. C.; Nicoll, K.; Anderson, S. W.

2007-05-01

Remote sensing datasets enable planetary volcanologists to extract information regarding eruption processes. Long-lived effusive eruptions at sites such as Kilauea Volcano (HI) provide opportunities to collect rich observational data sets, including detailed measurements of topography and extrusion rates, that allow comparisons between lava flow surface morphologies and emplacement conditions for use in interpreting similar morphological features associated with planetary lava flows. On Mars, the emplacement of basaltic lava flows is a volumetrically and spatially important process, creating both large-scale and small-scale surface morphologies. On Earth, low effusion rate eruptions on relatively horizontal slopes tend to create inflated lava flows that display hummocky topography. To better understand the processes involved in creating observed surface characteristics, we repeatedly measured the surface topography of an actively flowing and inflating basaltic unit within the Pu'u O'o flow field over a 5-day period. We used a ground-based laser-scanner (LiDAR) system that provided vertical and horizontal accuracies of 4 mm. Comparing DEMs from repeated laser scans yielded the magnitudes and styles of constructional processes, allowing us to quantify the relationship between pre- and post-emplacement surface topography. Our study site (roughly 200 m x 200 m) experienced about 5 m of vertical inflation over a 3 day period and created a new hummocky surface containing several tumuli. The temporal and spatial patterns of inflation were complex and showed no obvious relationship with underlying topography. High-precision morphometric measurements acquired using ground-based LiDAR affords us the opportunity to capture the essential boundary conditions necessary for evaluating and comparing high-resolution planetary data sets, such as those acquired by the MOC, HRSC, and HiRISE instruments.

Impact of plasma chemistry versus titanium surface topography on osteoblast orientation.

PubMed

Rebl, Henrike; Finke, Birgit; Lange, Regina; Weltmann, Klaus-Dieter; Nebe, J Barbara

2012-10-01

Topographical and chemical modifications of biomaterial surfaces both influence tissue physiology, but unfortunately little knowledge exists as to their combined effect. There are many indications that rough surfaces positively influence osteoblast behavior. Having determined previously that a positively charged, smooth titanium surface boosts osteoblast adhesion, we wanted to investigate the combined effects of topography and chemistry and elucidate which of these properties is dominant. Polished, machined and corundum-blasted titanium of increasing microroughness was additionally coated with plasma-polymerized allylamine (PPAAm). Collagen I was then immobilized using polyethylene glycol diacid and glutar dialdehyde. On all PPAAm-modified surfaces (i) adhesion of human MG-63 osteoblastic cells increased significantly in combination with roughness, (ii) cells resemble the underlying structure and melt with the surface, and (iii) cells overcome the restrictions of a grooved surface and spread out over a large area as indicated by actin staining. Interestingly, the cellular effects of the plasma-chemical surface modification are predominant over surface topography, especially in the initial phase. Collagen I, although it is the gold standard, does not improve surface adhesion features comparably. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Impact of the rheological layering of the lithosphere on the topography generated by sublithospheric density anomalies: Insights from analog modeling

NASA Astrophysics Data System (ADS)

Sembroni, A.; Globig, J.; Rozel, A.; Faccenna, C.; Funiciello, F.; Fernandez, M.

2013-12-01

Density anomalies located beneath the lithosphere are thought to generate dynamic topography at the surface of the Earth. Tomographic models are often used to infer the later variations of the density field in the mantle. Surface topography can then be computed using analytical solutions or numerical simulations of mantle convection. It has been shown that the viscosity profile of the upper mantle has a strong influence on the magnitude and spectral signature of surface topography and uplift rate. Here we present results from analogue modeling of the interaction between a rising ball-shaped density anomaly and the lithosphere in an isoviscous, isothermal Newtonian mantle system. Preliminary data show that surface topography is strongly influenced not only by mantle viscosity but also by density and viscosity profiles of the lithosphere. Our apparatus consists of a plexiglass square box (40x40x50 cm3) filled with glucose syrup. From the bottom a silicon ball was free to rise up until impinging a silicon plate floating on top of the syrup, mimicking the lithosphere. In order to investigate the role of lithospheric thickness and layered continental crust on stress partitioning, maximum dynamic topography, uplift rate and signal wavelength, two different configurations were tested: homogeneous lithosphere and stratified lithosphere including a low-viscosity lower crust. The topographic evolution of the surface was tracked using a laser scanning the top of the apparatus. The rise of the density anomaly was recorded by a side camera. We observe that a thick and then more resistant lithosphere makes up to 2 times lower and laterally wider topographic signatures. Layered lithospheres including a decoupling lower crust decrease the equilibrium topography and its lateral extend by ~30% to 40%. Most importantly, the uplift rate is strongly affected by the choice of lithosphere model. Both lithosphere width and the presence of a decoupling lower crust may modify the uplift rate by a factor 3. Thus, depending on the lithosphere rheology, we show that uplift rate may vary by one order of magnitude, for the same density anomaly and mantle viscosity. This result shows that surface uplift rate can be used to infer the viscosity of the upper mantle in specific Earth regions only if the rheology of the lithosphere is well constrained. With respect to previous approaches, whether numerical or analog modeling of dynamic topography, our experiments represent a new attempt to investigate the propagation of normal stresses generated by mantle flow through a rheologically stratified lithosphere and its resulting topographic signal.

Improved High Resolution Models of Subduction Dynamics: Use of transversely isotropic viscosity with a free-surface

NASA Astrophysics Data System (ADS)

Liu, X.; Gurnis, M.; Stadler, G.; Rudi, J.; Ratnaswamy, V.; Ghattas, O.

2017-12-01

Dynamic topography, or uncompensated topography, is controlled by internal dynamics, and provide constraints on the buoyancy structure and rheological parameters in the mantle. Compared with other surface manifestations such as the geoid, dynamic topography is very sensitive to shallower and more regional mantle structure. For example, the significant dynamic topography above the subduction zone potentially provides a rich mine for inferring the rheological and mechanical properties such as plate coupling, flow, and lateral viscosity variations, all critical in plate tectonics. However, employing subduction zone topography in the inversion study requires that we have a better understanding of the topography from forward models, especially the influence of the viscosity formulation, numerical resolution, and other factors. One common approach to formulating a fault between the subducted slab and the overriding plates in viscous flow models assumes a thin weak zone. However, due to the large lateral variation in viscosity, topography from free-slip numerical models typically has artificially large magnitude as well as high-frequency undulations over subduction zone, which adds to the difficulty in making comparisons between model results and observations. In this study, we formulate a weak zone with the transversely isotropic viscosity (TI) where the tangential viscosity is much smaller than the viscosity in the normal direction. Similar with isotropic weak zone models, TI models effectively decouple subducted slabs from the overriding plates. However, we find that the topography in TI models is largely reduced compared with that in weak zone models assuming an isotropic viscosity. Moreover, the artificial `tooth paste' squeezing effect observed in isotropic weak zone models vanishes in TI models, although the difference becomes less significant when the dip angle is small. We also implement a free-surface condition in our numerical models, which has a smoothing effect on the topography. With the improved model configuration, we can use the adjoint inversion method in a high-resolution model and employ topography in addition to other observables such as the plate motion to infer critical mechanical and rheological parameters in the subduction zone.

Crustal Fractures of Ophir Planum

NASA Technical Reports Server (NTRS)

2002-01-01

(Released 29 April 2002) The Science This THEMIS image covers a tract of plateau territory called Ophir Planum. The most obvious features in this scene are the fractures (ranging from 1 to 5 km wide) running from the upper left to lower right. Localized rifting and deep-seated tension fracturing of the crust probably formed these cracks. The wall rock displayed in the upper part of the cliffs appears to be layered. The southwest-facing wall of the largest and uppermost fracture has classic spur and gully topography. This type of topography is created by differing amounts of erosion. Also seen in this image are some scattered impact craters and some dark wind streaks in the lower right. The Ophir Planum plateau separates two separate smaller canyon systems, not visible in this image, (Candor Chasma to the north and Melas Chasma to the south) in the Valles Marineris canyon complex. The whole Valles Marineris canyon system extends some 4,000 km across the equatorial realms of Mars. For comparison, this would stretch from New York City to San Francisco. The Story Plateaus and spurs might make you think of cowboys on the open plain. 'Spurs' in this context, however, are simply ridges that can be seen on the side of the southwest-facing wall of the large fracture that splits the terrain. Gullies stretch down this slope as well. Both of these features are caused by erosion, which is a mild force of change compared to whatever tension cracked the crust and ripped apart the land. The wall rock displayed in the upper part of the cliffs appears to be layered, suggesting that different kinds of rocks and minerals can be found in each banded zone. The Ophir Planum plateau separates two separate canyon systems in the Valles Marineris complex, the largest canyon in the solar system. If Valles Marineris were on Earth, it would stretch from New York City all the way to San Francisco. That will give you some idea of the geological forces that have acted upon the planet over time. Look for scattered impact craters and some dark wind streaks in the deep dark terrain (lower right) as well.

An Investigation of Concrete Deterioration at South Florida Water Management District Structure S65E

DTIC Science & Technology

2014-02-01

24 Figure 19. SEM micrographs of deterioration observed on fracture surface including borehole near exposed surface and transition between...photomicrographs of repaired concrete surface. ........................................ 36 Figure A6. Supplemental photomicrographs of fractured sample...38 Figure B1. Supplemental SEM micrographs of inner non-deteriorated concrete fracture surface

Impact of lithospheric rheology on surface topography

NASA Astrophysics Data System (ADS)

Liao, K.; Becker, T. W.

2017-12-01

The expression of mantle flow such as due to a buoyant plume as surface topography is a classical problem, yet the role of rheological complexities could benefit from further exploration. Here, we investigate the topographic expressions of mantle flow by means of numerical and analytical approaches. In numerical modeling, both conventional, free-slip and more realistic, stress-free boundary conditions are applied. For purely viscous rheology, a high viscosity lithosphere will lead to slight overestimates of topography for certain settings, which can be understood by effectively modified boundary conditions. Under stress-free conditions, numerical and analytical results show that the magnitude of dynamic topography decreases with increasing lithosphere thickness (L) and viscosity (ηL), as L-1 and ηL-3. The wavelength of dynamic topography increases linearly with L and (ηL/ ηM) 1/3. We also explore the time-dependent interactions of a rising plume with the lithosphere. For a layered lithosphere with a decoupling weak lower crust embedded between stronger upper crust and lithospheric mantle, dynamic topography increases with a thinner and weaker lower crust. The dynamic topography saturates when the decoupling viscosity is 3-4 orders lower than the viscosity of upper crust and lithospheric mantle. We further explore the role of visco-elastic and visco-elasto-plastic rheologies.

Radial orbit error reduction and sea surface topography determination using satellite altimetry

NASA Technical Reports Server (NTRS)

Engelis, Theodossios

1987-01-01

A method is presented in satellite altimetry that attempts to simultaneously determine the geoid and sea surface topography with minimum wavelengths of about 500 km and to reduce the radial orbit error caused by geopotential errors. The modeling of the radial orbit error is made using the linearized Lagrangian perturbation theory. Secular and second order effects are also included. After a rather extensive validation of the linearized equations, alternative expressions of the radial orbit error are derived. Numerical estimates for the radial orbit error and geoid undulation error are computed using the differences of two geopotential models as potential coefficient errors, for a SEASAT orbit. To provide statistical estimates of the radial distances and the geoid, a covariance propagation is made based on the full geopotential covariance. Accuracy estimates for the SEASAT orbits are given which agree quite well with already published results. Observation equations are develped using sea surface heights and crossover discrepancies as observables. A minimum variance solution with prior information provides estimates of parameters representing the sea surface topography and corrections to the gravity field that is used for the orbit generation. The simulation results show that the method can be used to effectively reduce the radial orbit error and recover the sea surface topography.

Time-dependent effects of heat advection and topography on cooling histories during erosion

NASA Astrophysics Data System (ADS)

Mancktelow, Neil S.; Grasemann, Bernhard

1997-03-01

Both erosion and surface topography cause a time-dependent variation in isotherm geometry that can result in significant errors in estimating natural exhumation rates from geochronologic data. Analytical solutions and two-dimensional numerical modelling are used to investigate the magnitude of these inaccuracies for conditions appropriate to many rapidly exhumed mountain chains of rugged relief. It is readily demonstrated that uplift of the topographic surface has a negligible effect on the cooling history of an exhumed rock sample and cannot be quantified by current geochronologic methods. The topography itself perturbs the isotherms to a depth that depends on both the vertical and horizontal scale of the surface relief. Estimations employing different isotopic systems in the same sample with higher closure temperatures (> 200°C) are not generally influenced by topography. However, direct conversion of cooling rates to exhumation rates assuming a simple constant linear geotherm markedly underestimates peak rates, due to variation of the geothermal gradient in time and space and to the time lag between exhumation and cooling. Estimations based on the altitude variation in apatite fission-track ages are less prone to such inaccuracies in geothermal gradient but are affected by near-surface time-dependent variation in isotherm depth due to advection and topography. In tectonically active mountain belts, high exhumation rates are coupled with rugged topography, and exhumation rates may be markedly overestimated, by factors of 2 or more. Even at lower exhumation rates on the order of 1 mm/a, the shape of the cooling curve is modified by advection and topography. A convex-concave shape to the cooling curve does not necessarily imply a change of exhumation rate; it may also be attained by a more complicated geothermal gradient induced by topographic relief. Very fast cooling below 100°C, often interpreted as reflecting faster exhumation, can be more simply explained by the lateral cooling effect of topographic relief, with samples exhumed in valleys displaying a different near-surface cooling history to those on ridge crests.

The effect of glycerin solution density and viscosity on vibration amplitude of oblique different piezoelectric MC near the surface in 3D modeling

NASA Astrophysics Data System (ADS)

Korayem, A. H.; Abdi, M.; Korayem, M. H.

2018-06-01

The surface topography in nanoscale is one of the most important applications of AFM. The analysis of piezoelectric microcantilevers vibration behavior is essential to improve the AFM performance. To this end, one of the appropriate methods to simulate the dynamic behavior of microcantilever (MC) is a numerical solution with FEM in the 3D modeling using COMSOL software. The present study aims to simulate different geometries of the four-layered AFM piezoelectric MCs in 2D and 3D modeling in a liquid medium using COMSOL software. The 3D simulation was done in a spherical container using FSI domain in COMSOL. In 2D modeling by applying Hamilton's Principle based on Euler-Bernoulli Beam theory, the governing motion equation was derived and discretized with FEM. In this mode, the hydrodynamic force was assumed with a string of spheres. The effect of this force along with the squeezed-film force was considered on MC equations. The effect of fluid density and viscosity on the MC vibrations that immersed in different glycerin solutions was investigated in 2D and 3D modes and the results were compared with the experimental results. The frequencies and time responses of MC close to the surface were obtained considering tip-sample forces. The surface topography of MCs different geometries were compared in the liquid medium and the comparison was done in both tapping and non-contact mode. Various types of surface roughness were considered in the topography for MC different geometries. Also, the effect of geometric dimensions on the surface topography was investigated. In liquid medium, MC is installed at an oblique position to avoid damaging the MC due to the squeezed-film force in the vicinity of MC surface. Finally, the effect of MC's angle on surface topography and time response of the system was investigated.

Optimal leveling of flow over one-dimensional topography by Marangoni stresses

NASA Astrophysics Data System (ADS)

Gramlich, C. M.; Kalliadasis, Serafim; Homsy, G. M.; Messer, C.

2002-06-01

A thin viscous film flowing over a step down in topography exhibits a capillary ridge preceding the step. In applications, a planar liquid surface is often desired and hence there is a need to level the ridge. This paper investigates optimal leveling of the ridge by means of a Marangoni stress such as might be produced by a localized heater creating temperature variations at the film surface. The differential equation for the free surface based on lubrication theory and incorporating the effects of topography and temperature gradients is solved numerically for steps down in topography with different temperature profiles. Both rectangular "top-hat" and parabolic profiles, chosen to model physically realizable heaters, were found to be effective in reducing the height of the capillary ridge. Leveling the ridge is formulated as an optimization problem to minimize the maximum free-surface height by varying the heater strength, position, and width. With the optimized heaters, the variation in surface height is reduced by more than 50% compared to the original isothermal ridge. For more effective leveling, we consider an asymmetric n-step temperature distribution. The optimal n-step heater in this case results in (n+1) ridges of equal size; 2- and 3-step heaters reduce the variation in surface height by about 70% and 77%, respectively. Finally, we explore the potential of coolers and step temperature profiles for still more effective leveling.

Coevolution of bed surface patchiness and channel morphology: 2. Numerical experiments

USGS Publications Warehouse

Nelson, Peter A.; McDonald, Richard R.; Nelson, Jonathan M.; Dietrich, William E.

2015-01-01

In gravel bed rivers, bed topography and the bed surface grain size distribution evolve simultaneously, but it is not clear how feedbacks between topography and grain sorting affect channel morphology. In this, the second of a pair of papers examining interactions between bed topography and bed surface sorting in gravel bed rivers, we use a two-dimensional morphodynamic model to perform numerical experiments designed to explore the coevolution of both free and forced bars and bed surface patches. Model runs were carried out on a computational grid simulating a 200 m long, 2.75 m wide, straight, rectangular channel, with an initially flat bed at a slope of 0.0137. Over five numerical experiments, we varied (a) whether an obstruction was present, (b) whether the sediment was a gravel mixture or a single size, and (c) whether the bed surface grain size feeds back on the hydraulic roughness field. Experiments with channel obstructions developed a train of alternate bars that became stationary and were connected to the obstruction. Freely migrating alternate bars formed in the experiments without channel obstructions. Simulations incorporating roughness feedbacks between the bed surface and flow field produced flatter, broader, and longer bars than simulations using constant roughness or uniform sediment. Our findings suggest that patches are not simply a by-product of bed topography, but they interact with the evolving bed and influence morphologic evolution.

The Effect of Surface Ice and Topography on the Atmospheric Circulation and Distribution of Nitrogen Ice on Pluto

NASA Astrophysics Data System (ADS)

Rafkin, Scot C. R.; Soto, Alejandro; Michaels, Timothy I.

2016-10-01

A newly developed general circulation model (GCM) for Pluto is used to investigate the impact of a heterogeneous distribution of nitrogen surface ice and large scale topography on Pluto's atmospheric circulation. The GCM is based on the GFDL Flexible Modeling System (FSM). Physics include a gray model radiative-conductive scheme, subsurface conduction, and a nitrogen volatile cycle. The radiative-conductive model takes into account the 2.3, 3.3 and 7.8 μm bands of CH4 and CO, including non-local thermodynamic equilibrium effects. including non-local thermodynamic equilibrium effects. The nitrogen volatile cycle is based on a vapor pressure equilibrium assumption between the atmosphere and surface. Prior to the arrival of the New Horizons spacecraft, the expectation was that the volatile ice distribution on the surface of Pluto would be strongly controlled by the latitudinal temperature gradient. If this were the case, then Pluto would have broad latitudinal bands of both ice covered surface and ice free surface, as dictated by the season. Further, the circulation, and the thus the transport of volatiles, was thought to be driven almost exclusively by sublimation and deposition flows associated with the volatile cycle. In contrast to expectations, images from New Horizon showed an extremely complex, heterogeneous distribution of surface ices draped over substantial and variable topography. To produce such an ice distribution, the atmospheric circulation and volatile transport must be more complex than previously envisioned. Simulations where topography, surface ice distributions, and volatile cycle physics are added individually and in various combinations are used to individually quantify the importance of the general circulation, topography, surface ice distributions, and condensation flows. It is shown that even regional patches of ice or large craters can have global impacts on the atmospheric circulation, the volatile cycle, and hence, the distribution of surface ices. The work demonstrates that explaining Pluto's volatile cycle and the expression of that cycle in the surface ice distributions requires consideration of atmospheric processes beyond simple vapor pressure equilibrium arguments.

Characterizing Arctic Sea Ice Topography Using High-Resolution IceBridge Data

NASA Technical Reports Server (NTRS)

Petty, Alek; Tsamados, Michel; Kurtz, Nathan; Farrell, Sinead; Newman, Thomas; Harbeck, Jeremy; Feltham, Daniel; Richter-Menge, Jackie

2016-01-01

We present an analysis of Arctic sea ice topography using high resolution, three-dimensional, surface elevation data from the Airborne Topographic Mapper, flown as part of NASA's Operation IceBridge mission. Surface features in the sea ice cover are detected using a newly developed surface feature picking algorithm. We derive information regarding the height, volume and geometry of surface features from 2009-2014 within the Beaufort/Chukchi and Central Arctic regions. The results are delineated by ice type to estimate the topographic variability across first-year and multi-year ice regimes.

Effects of patterned topography on biofilm formation

NASA Astrophysics Data System (ADS)

Vasudevan, Ravikumar

2011-12-01

Bacterial biofilms are a population of bacteria attached to each other and irreversibly to a surface, enclosed in a matrix of self-secreted polymers, among others polysaccharides, proteins, DNA. Biofilms cause persisting infections associated with implanted medical devices and hospital acquired (nosocomial) infections. Catheter-associated urinary tract infections (CAUTIs) are the most common type of nosocomial infections accounting for up to 40% of all hospital acquired infections. Several different strategies, including use of antibacterial agents and genetic cues, quorum sensing, have been adopted for inhibiting biofilm formation relevant to CAUTI surfaces. Each of these methods pertains to certain types of bacteria, processes and has shortcomings. Based on eukaryotic cell topography interaction studies and Ulva linza spore studies, topographical surfaces were suggested as a benign control method for biofilm formation. However, topographies tested so far have not included a systematic variation of size across basic topography shapes. In this study patterned topography was systematically varied in size and shape according to two approaches 1) confinement and 2) wetting. For the confinement approach, using scanning electron microscopy and confocal microscopy, orienting effects of tested topography based on staphylococcus aureus (s. aureus) (SH1000) and enterobacter cloacae (e. cloacae) (ATCC 700258) bacterial models were identified on features of up to 10 times the size of the bacterium. Psuedomonas aeruginosa (p. aeruginosa) (PAO1) did not show any orientational effects, under the test conditions. Another important factor in medical biofilms is the identification and quantification of phenotypic state which has not been discussed in the literature concerning bacteria topography characterizations. This was done based on antibiotic susceptibility evaluation and also based on gene expression analysis. Although orientational effects occur, phenotypically no difference was observed between the patterned topography tested. Another potential strategy for biofilm control through patterned topography is based on the design of robust non-wetting surfaces with undercut feature geometries, characterized by 1) breakthrough pressure and 2) triple phase contact line model. It was found that height and presence of undercut had statistically significant effects, directly proportional to breakthrough pressures, whereas extent of undercut did not. A predictive triple phase contact line model was also developed. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

Effect of root planing on surface topography: an in-vivo randomized experimental trial.

PubMed

Rosales-Leal, J I; Flores, A B; Contreras, T; Bravo, M; Cabrerizo-Vílchez, M A; Mesa, F

2015-04-01

The root surface topography exerts a major influence on clinical attachment and bacterial recolonization after root planing. In-vitro topographic studies have yielded variable results, and clinical studies are necessary to compare root surface topography after planing with current ultrasonic devices and with traditional manual instrumentation. The aim of this study was to compare the topography of untreated single-rooted teeth planed in vivo with a curette, a piezoelectric ultrasonic (PU) scraper or a vertically oscillating ultrasonic (VOU) scraper. In a randomized experimental trial of 19 patients, 44 single-rooted teeth were randomly assigned to one of four groups for: no treatment; manual root planing with a curette; root planing with a PU scraper; or root planing with a VOU scraper. Post-treatment, the teeth were extracted and their topography was analyzed in 124 observations with white-light confocal microscopy, measuring the roughness parameters arithmetic average height, root-mean-square roughness, maximum height of peaks, maximum depth of valleys, absolute height, skewness and kurtosis. The roughness values arithmetic average height and root-mean-square roughness were similar after each treatment and lower than after no treatment ( p < 0.05). Absolute height was lower in the VOU group than in the untreated ( p = 0.0026) and PU (p = 0.045) groups. Surface morphology was similar after the three treatments and was less irregular than in the untreated group. Values for the remaining roughness parameters were similar among all treatment groups ( p > 0.05). Both ultrasonic devices reduce the roughness, producing a similar topography to that observed after manual instrumentation with a curette, to which they appear to represent a valid alternative. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

A Synthesis and Comparison of Approaches for Quantifying Coral Reef Structure

NASA Astrophysics Data System (ADS)

Duvall, M. S.; Hench, J. L.

2016-02-01

The complex physical structures of coral reefs provide substrate for benthic organisms, surface area for material fluxes, and have been used as a predictor of reef-fish biomass and biodiversity. Coral reef topography has a first order effect on reef hydrodynamics by imposing drag forces and increasing momentum and scalar dispersion. Despite its importance, quantifying reef topography remains a challenge, as it is patchy and discontinuous while also varying over orders of magnitude in spatial scale. Previous studies have quantified reef structure using a range of 1D and 2D metrics that estimate vertical roughness, which is the departure from a flat geometric profile or surface. However, there is no general mathematical or conceptual framework by which to apply or compare these roughness metrics. While the specific calculations of different metrics vary, we propose that they can be classified into four categories based on: 1) vertical relief relative to a reference height; 2) gradients in vertical relief; 3) surface contour distance; or 4) variations in roughness with scale. We apply metrics from these four classes to idealized reef topography as well as natural reef topography data from Moorea, French Polynesia. Through the use of idealized profiles, we demonstrate the potential for reefs with different morphologies to possess the same value for some scale-dependent metrics (i.e. classes 1-3). Due to the superposition of variable-scale roughness elements in reef topography, we find that multi-scale metrics (i.e. class 4) can better characterize structural complexity by capturing surface roughness across a range of spatial scales. In particular, we provide evidence of the ability of 1D continuous wavelet transforms to detect changes in dominant roughness scales on idealized topography as well as within real reef systems.

Optimal leveling of flow over one-dimensional topography by Marangoni stresses

NASA Astrophysics Data System (ADS)

Gramlich, C. M.; Homsy, G. M.; Kalliadasis, Serafim

2001-11-01

A thin viscous film flowing over a step down in topography exhibits a capillary ridge near the step, which may be undesirable in applications. This paper investigates optimal leveling of the ridge by means of a Marangoni stress such as might be produced by a localized heater creating temperature variations at the film surface. Lubrication theory results in a differential equation for the free surface, which can be solved numerically for any given topography and temperature profile. Leveling the ridge is then formulated as an optimization problem to minimize the maximum free-surface height by varying the heater strength, position, and width. Optimized heaters with 'top-hat' or parabolic temperature profiles replace the original ridge with two smaller ridges of equal size, achieving leveling of better than 50%. An optimized asymmetric n-step temperature distribution results in (n+1) ridges and reduces the variation in surface height by a factor of better than 1/(n+1).

KSC-08pd1656

NASA Image and Video Library

2008-05-06

VANDENBERG AIR FORCE BASE, Calif. – The Ocean Surface Topography Mission, or OSTM/Jason 2, spacecraft is being prepared for bagging before encapsulation and transfer to the launch pad. The launch of the Ocean Surface Topography Mission, or OSTM/Jason 2, aboard a Delta II rocket is scheduled for Friday, June 20, from Vandenberg Air Force Base in California. The launch window extends from 12:46 a.m. to 12:55 a.m. PDT. The satellite will be placed in an 830-mile-high orbit at an inclination of 66 degrees after separating from the Delta II 55 minutes after liftoff. The five primary science instruments of the Ocean Surface Topography Mission aboard the Jason 2 spacecraft are dedicated to measuring ocean surface height. These measurements will be used to evaluate and forecast climate changes and improve weather forecasting. The results also are expected to help forecasters better predict hurricane intensity. Photo credit: NASA

KSC-08pd1658

NASA Image and Video Library

2008-05-06

VANDENBERG AIR FORCE BASE, Calif. – The Ocean Surface Topography Mission, or OSTM/Jason 2, spacecraft is being prepared for bagging before encapsulation and transfer to the launch pad. The launch of the Ocean Surface Topography Mission, or OSTM/Jason 2, aboard a Delta II rocket is scheduled for Friday, June 20, from Vandenberg Air Force Base in California. The launch window extends from 12:46 a.m. to 12:55 a.m. PDT. The satellite will be placed in an 830-mile-high orbit at an inclination of 66 degrees after separating from the Delta II 55 minutes after liftoff. The five primary science instruments of the Ocean Surface Topography Mission aboard the Jason 2 spacecraft are dedicated to measuring ocean surface height. These measurements will be used to evaluate and forecast climate changes and improve weather forecasting. The results also are expected to help forecasters better predict hurricane intensity. Photo credit: NASA

KSC-08pd1655

NASA Image and Video Library

2008-05-06

VANDENBERG AIR FORCE BASE, Calif. – The Ocean Surface Topography Mission, or OSTM/Jason 2, spacecraft is being prepared for bagging before encapsulation and transfer to the launch pad. The launch of the Ocean Surface Topography Mission, or OSTM/Jason 2, aboard a Delta II rocket is scheduled for Friday, June 20, from Vandenberg Air Force Base in California. The launch window extends from 12:46 a.m. to 12:55 a.m. PDT. The satellite will be placed in an 830-mile-high orbit at an inclination of 66 degrees after separating from the Delta II 55 minutes after liftoff. The five primary science instruments of the Ocean Surface Topography Mission aboard the Jason 2 spacecraft are dedicated to measuring ocean surface height. These measurements will be used to evaluate and forecast climate changes and improve weather forecasting. The results also are expected to help forecasters better predict hurricane intensity. Photo credit: NASA

KSC-08pd1657

NASA Image and Video Library

2008-05-06

VANDENBERG AIR FORCE BASE, Calif. – The Ocean Surface Topography Mission, or OSTM/Jason 2, spacecraft is being prepared for bagging before encapsulation and transfer to the launch pad. The launch of the Ocean Surface Topography Mission, or OSTM/Jason 2, aboard a Delta II rocket is scheduled for Friday, June 20, from Vandenberg Air Force Base in California. The launch window extends from 12:46 a.m. to 12:55 a.m. PDT. The satellite will be placed in an 830-mile-high orbit at an inclination of 66 degrees after separating from the Delta II 55 minutes after liftoff. The five primary science instruments of the Ocean Surface Topography Mission aboard the Jason 2 spacecraft are dedicated to measuring ocean surface height. These measurements will be used to evaluate and forecast climate changes and improve weather forecasting. The results also are expected to help forecasters better predict hurricane intensity. Photo credit: NASA

The relationship between surface topography, gravity anomalies, and temperature structure of convection

NASA Technical Reports Server (NTRS)

Parsons, B.; Daly, S.

1983-01-01

Consideration is given to the relationship between the temperature structure of mantle convection and the resulting surface topography and gravity anomalies, which are used in its investigation. Integral expressions relating the three variables as a function of wavelength are obtained with the use of Green's function solutions to the equations of motion for the case of constant-viscosity convection in a plane layer subject to a uniform gravitational field. The influence of the boundary conditions, particularly at large wavelengths, is pointed out, and surface topographies and gravity produced by convection are illustrated for a number of simple temperature distributions. It is shown that the upper thermal boundary layer plays an important role in determining the surface observables, while temperatures near the bottom of the layer affect mainly that boundary. This result is consistent with an explanation of geoid anomalies over mid-ocean swells in terms of convection beneath the lithosphere.

Design and construction of a novel tribometer with online topography and wear measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korres, Spyridon; Dienwiebel, Martin

2010-06-15

We present a novel experimental platform that links topographical and material changes with the friction and wear behavior of oil-lubricated metal surfaces. This concept combines state-of-the-art methods for the analysis of the surface topography on the micro- and nanoscale with the online measurement of wear. At the same time, it allows for frictional and lateral force detection. Information on the topography of one of the two surfaces is gathered in situ with a three-dimensional (3D) holography microscope at a maximum frequency of 15 frames/s and higher resolution images are provided at defined time intervals by an atomic force microscope. Themore » wear measurement is conducted online by means of radio nuclide technique. The quantitative measurement of the lateral and frictional forces is conducted with a custom-built 3D force sensor. The surfaces can be lubricated with an optically transparent oil or water. The stability and precision of the setup have been tested in a model experiment. The results show that the exact same position can be relocated and examined after each load cycle. Wear and topography measurements were performed with a radioactive labeled iron pin sliding against an iron plate.« less

Biomechanical properties of jaw periosteum-derived mineralized culture on different titanium topography.

PubMed

Att, Wael; Kubo, Katsutoshi; Yamada, Masahiro; Maeda, Hatsuhiko; Ogawa, Takahiro

2009-01-01

This study evaluated the biomechanical properties of periosteum-derived mineralized culture on different surface topographies of titanium. Titanium surfaces modified by machining or by acid etching were analyzed using scanning electron microscopy (SEM). Rat mandibular periosteum-derived cells were cultured on either of the titanium surfaces. Cell proliferation was evaluated by cell counts, and gene expression was analyzed using a reverse-transcriptase polymerase chain reaction. Alkaline phosphatase (ALP) stain assay was employed to evaluate osteoblastic activity. Matrix mineralization was examined via von Kossa stain assay, total calcium deposition, and SEM. The hardness and elastic modulus of mineralized cultures were measured using a nano-indenter. The machined surface demonstrated a flat topographic configuration, while the acid-etched surface revealed a uniform micron-scale roughness. Both cell density and ALP activity were significantly higher on the machined surface than on the acid-etched surface. The expression of bone-related genes was up-regulated or enhanced on the acid-etched surface compared to the machined surface. Von Kossa stain showed significantly greater positive areas for the machined surface compared to the acid-etched surface, while total calcium deposition was statistically similar. Mineralized culture on the acid-etched surface was characterized by denser calcium deposition, more mature collagen deposition on the superficial layer, and larger and denser globular matrices inside the matrix than the culture on the machined surface. The mineralized matrix on the acid-etched surface was two times harder than on the machined surface, whereas the elastic modulus was comparable between the two surfaces. The design of this study can be used as a model to evaluate the effect of implant surface topography on the biomechanical properties of periosteum-derived mineralized culture. The results suggest that mandibular periosteal cells respond to different titanium surface topographies differently enough to produce mineralized matrices with different biomechanical qualities.

The Role of Membrane Curvature in Nanoscale Topography-Induced Intracellular Signaling.

PubMed

Lou, Hsin-Ya; Zhao, Wenting; Zeng, Yongpeng; Cui, Bianxiao

2018-05-15

Over the past decade, there has been growing interest in developing biosensors and devices with nanoscale and vertical topography. Vertical nanostructures induce spontaneous cell engulfment, which enhances the cell-probe coupling efficiency and the sensitivity of biosensors. Although local membranes in contact with the nanostructures are found to be fully fluidic for lipid and membrane protein diffusions, cells appear to actively sense and respond to the surface topography presented by vertical nanostructures. For future development of biodevices, it is important to understand how cells interact with these nanostructures and how their presence modulates cellular function and activities. How cells recognize nanoscale surface topography has been an area of active research for two decades before the recent biosensor works. Extensive studies show that surface topographies in the range of tens to hundreds of nanometers can significantly affect cell functions, behaviors, and ultimately the cell fate. For example, titanium implants having rough surfaces are better for osteoblast attachment and host-implant integration than those with smooth surfaces. At the cellular level, nanoscale surface topography has been shown by a large number of studies to modulate cell attachment, activity, and differentiation. However, a mechanistic understanding of how cells interact and respond to nanoscale topographic features is still lacking. In this Account, we focus on some recent studies that support a new mechanism that local membrane curvature induced by nanoscale topography directly acts as a biochemical signal to induce intracellular signaling, which we refer to as the curvature hypothesis. The curvature hypothesis proposes that some intracellular proteins can recognize membrane curvatures of a certain range at the cell-to-material interface. These proteins then recruit and activate downstream components to modulate cell signaling and behavior. We discuss current technologies allowing the visualization of membrane deformation at the cell membrane-to-substrate interface with nanometer precision and demonstrate that vertical nanostructures induce local curvatures on the plasma membrane. These local curvatures enhance the process of clathrin-mediated endocytosis and affect actin dynamics. We also present evidence that vertical nanostructures can induce significant deformation of the nuclear membrane, which can affect chromatin distribution and gene expression. Finally, we provide a brief perspective on the curvature hypothesis and the challenges and opportunities for the design of nanotopography for manipulating cell behavior.

Interferometer for measuring dynamic corneal topography

NASA Astrophysics Data System (ADS)

Micali, Jason Daniel

The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. It is desirable to possess an instrument that can measure the corneal shape and tear film surface with the same accuracy and resolution that is currently performed on common optical elements. A dual interferometer system for measuring the dynamic corneal topography is designed, built, and verified. The completed system is validated by testing on human subjects. The system consists of two co-aligned polarization splitting Twyman-Green interferometers designed to measure phase instantaneously. The primary interferometer measures the surface of the tear film while the secondary interferometer simultaneously tracks the absolute position of the cornea. Eye motion, ocular variation, and a dynamic tear film surface will result in a non-null configuration of the surface with respect to the interferometer system. A non-null test results in significant interferometer induced errors that add to the measured phase. New algorithms are developed to recover the absolute surface topography of the tear film and corneal surface from the simultaneous interferometer measurements. The results are high-resolution and high-accuracy surface topography measurements of the in vivo cornea that are captured at standard camera frame rates. This dissertation will cover the development and construction of an interferometer system for measuring the dynamic corneal topography of the human eye. The discussion starts with the completion of an interferometer for measuring the tear film. The tear film interferometer is part of an ongoing research project that has spanned multiple dissertations. For this research, the instrument was tested on human subjects and resulted in refinements to the interferometer design. The final configuration of the tear film interferometer and results from human subjects testing are presented. Feedback from this instrument was used to support the development and construction of the interferometric corneal topographer system. A calibration is performed on the instrument, and then verified against simulated eye surfaces. Finally, the instrument is validated by testing on human subjects. The result is an interferometer system that can non-invasively measure the dynamic corneal topography with greater accuracy and resolution than existing technologies.

Modification of the Surface Properties of Polyimide Films using POSS Deposition and Oxygen Plasma Exposure

NASA Technical Reports Server (NTRS)

Wohl, Christopher J.; Belcher, Marcus A.; Ghose, Sayata; Connell, John W.

2008-01-01

Topographically rich surfaces were generated by spray-coating organic solutions of a polyhedral oligomeric silsesquioxane, octakis (dimethylsilyloxy) silsesquioxane (POSS), on Kapton HN films and exposing them to radio frequency generated oxygen plasma. Changes in both surface chemistry and topography were observed. High-resolution scanning electron microscopy indicated substantial modification of the POSS-coated polyimide surface topographies as a result of oxygen plasma exposure. Water contact angles varied from 104 deg for unexposed POSS-coated surfaces to approximately 5 deg, for samples exposed for 5 h. Modulation of the dispersive and polar contributions to the surface energy was determined using van Oss Good Chaudhury theory.

Contribution of thermal infrared images on the understanding of the subsurface/atmosphere exchanges on Earth.

NASA Astrophysics Data System (ADS)

Lopez, Teodolina; Antoine, Raphaël; Baratoux, David; Rabinowicz, Michel

2017-04-01

High temporal resolution of space-based thermal infrared images (METEOSAT, MODIS) and the development of field thermal cameras have permitted the development of thermal remote sensing in Earth Sciences. Thermal images are influenced by many factors such as atmosphere, solar radiation, topography and physico-chemical properties of the surface. However, considering these limitations, we have discovered that thermal images can be used in order to better understand subsurface hydrology. In order to reduce as much as possible the impact of these perturbing factors, our approach combine 1) field observations and 2) numerical modelling of surface/subsurface thermal processes. Thermal images of the Piton de la Fournaise volcano (Réunion Island), acquired by hand, show that the Formica Leo inactive scoria cone and some fractures close to the Bory-Dolomieu caldera are always warmer, inducing a thermal difference with the surrounding of at least 5°C and a Self-Potential anomaly [1, 2]. Topography cannot explain this thermal behaviour, but Piton de la Fournaise is known as highly permeable. This fact allows the development of an air convection within the whole permeable structure volcanic edifice [2]. Cold air enters the base of the volcano, and exits warmer upslope, as the air is warmed by the geothermal flow [1,2]. Then, we have decided to understand the interaction between subsurface hydrogeological flows and the humidity in the atmosphere. In the Lake Chad basin, regions on both sides of Lake Chad present a different thermal behaviour during the diurnal cycle and between seasons [3]. We propose that this thermal behaviour can only be explained by lateral variations of the surface permeability that directly impact the process of evaporation/condensation cycle. These studies bring new highlights on the understanding of the exchanges between subsurface and the atmosphere, as the presence of a very permeable media and/or variations of the surface permeability may enhance or not the evaporation/condensation cycle. [1] Antoine et al. (2009). J. Volcanol. Geotherm. Res., 183(3-4), 228-1140. [2] Antoine et al. (2017). Geothermics, 65, 81-98. [3] Lopez et al. (2016). Surv. Geophys., 37 (2), 471-502.

Reproducibility of UAV-based earth surface topography based on structure-from-motion algorithms.

NASA Astrophysics Data System (ADS)

Clapuyt, François; Vanacker, Veerle; Van Oost, Kristof

2014-05-01

A representation of the earth surface at very high spatial resolution is crucial to accurately map small geomorphic landforms with high precision. Very high resolution digital surface models (DSM) can then be used to quantify changes in earth surface topography over time, based on differencing of DSMs taken at various moments in time. However, it is compulsory to have both high accuracy for each topographic representation and consistency between measurements over time, as DSM differencing automatically leads to error propagation. This study investigates the reproducibility of reconstructions of earth surface topography based on structure-from-motion (SFM) algorithms. To this end, we equipped an eight-propeller drone with a standard reflex camera. This equipment can easily be deployed in the field, as it is a lightweight, low-cost system in comparison with classic aerial photo surveys and terrestrial or airborne LiDAR scanning. Four sets of aerial photographs were created for one test field. The sets of airphotos differ in focal length, and viewing angles, i.e. nadir view and ground-level view. In addition, the importance of the accuracy of ground control points for the construction of a georeferenced point cloud was assessed using two different GPS devices with horizontal accuracy at resp. the sub-meter and sub-decimeter level. Airphoto datasets were processed with SFM algorithm and the resulting point clouds were georeferenced. Then, the surface representations were compared with each other to assess the reproducibility of the earth surface topography. Finally, consistency between independent datasets is discussed.

Influence of Fiber Orientation on Single-Point Cutting Fracture Behavior of Carbon-Fiber/Epoxy Prepreg Sheets.

PubMed

Wei, Yingying; An, Qinglong; Cai, Xiaojiang; Chen, Ming; Ming, Weiwei

2015-10-02

The purpose of this article is to investigate the influences of carbon fibers on the fracture mechanism of carbon fibers both in macroscopic view and microscopic view by using single-point flying cutting method. Cutting tools with three different materials were used in this research, namely, PCD (polycrystalline diamond) tool, CVD (chemical vapor deposition) diamond thin film coated carbide tool and uncoated carbide tool. The influence of fiber orientation on the cutting force and fracture topography were analyzed and conclusions were drawn that cutting forces are not affected by cutting speeds but significantly influenced by the fiber orientation. Cutting forces presented smaller values in the fiber orientation of 0/180° and 15/165° but the highest one in 30/150°. The fracture mechanism of carbon fibers was studied in different cutting conditions such as 0° orientation angle, 90° orientation angle, orientation angles along fiber direction, and orientation angles inverse to the fiber direction. In addition, a prediction model on the cutting defects of carbon fiber reinforced plastic was established based on acoustic emission (AE) signals.

X-ray topographic fractography of single crystals of molybdenum and niobium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hmelo, A.B.

1982-12-01

The semi-brittle (001) cleavage fracture at 77/sup 0/K of Mo and outgassed Nb single crystals was related to their fracture toughness. Berg-Barrett x-ray reflection topography and White Beam Synchrotron Fractography were used. Calibrated electropolishing in layers followed by Synchrotron Fractography revealed that under the conditions which existed at the tip of the running crack, Mo underwent general yielding which resulted in a plastically curved lattice. This result correlates with the substantial fracture toughness for Mo measured previously. On the other hand, double (112) slip was observed for Nb. The plastic zone associated with the crack-tip is shown to have amore » structure typicla of shock-loaded materials, consisting of arrays of screw dislocations, micro- and macrotwins. This result correlates with the low fracture toughness of Nb at 77/sup 0/K. It is proposed that these extremes in cleavage behavior for Mo vs Nb can be rationalized in terms of the capacity of a bcc structure to undergo a slip to twinning transition at high strain rates. 32 figures, 5 tables.« less

Influence of Fiber Orientation on Single-Point Cutting Fracture Behavior of Carbon-Fiber/Epoxy Prepreg Sheets

PubMed Central

Wei, Yingying; An, Qinglong; Cai, Xiaojiang; Chen, Ming; Ming, Weiwei

2015-01-01

The purpose of this article is to investigate the influences of carbon fibers on the fracture mechanism of carbon fibers both in macroscopic view and microscopic view by using single-point flying cutting method. Cutting tools with three different materials were used in this research, namely, PCD (polycrystalline diamond) tool, CVD (chemical vapor deposition) diamond thin film coated carbide tool and uncoated carbide tool. The influence of fiber orientation on the cutting force and fracture topography were analyzed and conclusions were drawn that cutting forces are not affected by cutting speeds but significantly influenced by the fiber orientation. Cutting forces presented smaller values in the fiber orientation of 0/180° and 15/165° but the highest one in 30/150°. The fracture mechanism of carbon fibers was studied in different cutting conditions such as 0° orientation angle, 90° orientation angle, orientation angles along fiber direction, and orientation angles inverse to the fiber direction. In addition, a prediction model on the cutting defects of carbon fiber reinforced plastic was established based on acoustic emission (AE) signals. PMID:28793597

Lava flow field emplacement studies of Manua Ulu (Kilauea Volcano, Hawai'i, United States) and Venus, using field and remote sensing analyses

NASA Astrophysics Data System (ADS)

Byrnes, Jeffrey Myer

2002-04-01

This work examines lava emplacement processes by characterizing surface units using field and remote sensing analyses in order to understand the development of lava flow fields. Specific study areas are the 1969--1974 Mauna Ulu compound flow field, (Kilauea Volcano, Hawai'i, USA), and five lava flow fields on Venus: Turgmam Fluctus, Zipaltonal Fluctus, the Tuli Mons/Uilata Fluctus flow complex, the Var Mons flow field, and Mylitta Fluctus. Lava surface units have been examined in the field and with visible-, thermal-, and radar-wavelength remote sensing datasets for Mauna Ulu, and with radar data for the Venusian study areas. For the Mauna Ulu flow field, visible characteristics are related to color, glass abundance, and dm- to m-scale surface irregularities, which reflect the lava flow regime, cooling, and modification due to processes such as coalescence and inflation. Thermal characteristics are primarily affected by the abundance of glass and small-scale roughness elements (such as vesicles), and reflect the history of cooling, vesiculation and degassing, and crystallization of the lava. Radar characteristics are primarily affected by unit topography and fracturing, which are related to flow inflation, remobilization, and collapse, and reflect the local supply of lava during and after unit emplacement. Mauna Ulu surface units are correlated with pre-eruption topography, lack a simple relationship to the main feeder lava tubes, and are distributed with respect to their position within compound flow lobes and with distance from the vent. The Venusian lava flow fields appear to have developed through emplacement of numerous, thin, simple and compound flows, presumably over extended periods of time, and show a wider range of radar roughness than is observed at Mauna Ulu. A potential correlation is suggested between flow rheology and surface roughness. Distributary flow morphologies may result from tube-fed flows, and flow inflation is consistent with observed surface characteristics. Furthermore, the significance of inflation at Mauna Ulu and comparison of radar characteristics indicates that inflation may, in fact, be more prevalent on Venus than at Mauna Ulu. Although the Venusian flow fields display morphologies similar to those observed within terrestrial flow fields, the Venusian flow units are significantly larger.

Snap evaporation of droplets on smooth topographies.

PubMed

Wells, Gary G; Ruiz-Gutiérrez, Élfego; Le Lirzin, Youen; Nourry, Anthony; Orme, Bethany V; Pradas, Marc; Ledesma-Aguilar, Rodrigo

2018-04-11

Droplet evaporation on solid surfaces is important in many applications including printing, micro-patterning and cooling. While seemingly simple, the configuration of evaporating droplets on solids is difficult to predict and control. This is because evaporation typically proceeds as a "stick-slip" sequence-a combination of pinning and de-pinning events dominated by static friction or "pinning", caused by microscopic surface roughness. Here we show how smooth, pinning-free, solid surfaces of non-planar topography promote a different process called snap evaporation. During snap evaporation a droplet follows a reproducible sequence of configurations, consisting of a quasi-static phase-change controlled by mass diffusion interrupted by out-of-equilibrium snaps. Snaps are triggered by bifurcations of the equilibrium droplet shape mediated by the underlying non-planar solid. Because the evolution of droplets during snap evaporation is controlled by a smooth topography, and not by surface roughness, our ideas can inspire programmable surfaces that manage liquids in heat- and mass-transfer applications.

A three-dimensional Dirichlet-to-Neumann operator for water waves over topography

NASA Astrophysics Data System (ADS)

Andrade, D.; Nachbin, A.

2018-06-01

Surface water waves are considered propagating over highly variable non-smooth topographies. For this three dimensional problem a Dirichlet-to-Neumann (DtN) operator is constructed reducing the numerical modeling and evolution to the two dimensional free surface. The corresponding Fourier-type operator is defined through a matrix decomposition. The topographic component of the decomposition requires special care and a Galerkin method is provided accordingly. One dimensional numerical simulations, along the free surface, validate the DtN formulation in the presence of a large amplitude, rapidly varying topography. An alternative, conformal mapping based, method is used for benchmarking. A two dimensional simulation in the presence of a Luneburg lens (a particular submerged mound) illustrates the accurate performance of the three dimensional DtN operator.

Controlled surface topography regulates collective 3D migration by epithelial-mesenchymal composite embryonic tissues.

PubMed

Song, Jiho; Shawky, Joseph H; Kim, YongTae; Hazar, Melis; LeDuc, Philip R; Sitti, Metin; Davidson, Lance A

2015-07-01

Cells in tissues encounter a range of physical cues as they migrate. Probing single cell and collective migratory responses to physically defined three-dimensional (3D) microenvironments and the factors that modulate those responses are critical to understanding how tissue migration is regulated during development, regeneration, and cancer. One key physical factor that regulates cell migration is topography. Most studies on surface topography and cell mechanics have been carried out with single migratory cells, yet little is known about the spreading and motility response of 3D complex multi-cellular tissues to topographical cues. Here, we examine the response to complex topographical cues of microsurgically isolated tissue explants composed of epithelial and mesenchymal cell layers from naturally 3D organized embryos of the aquatic frog Xenopus laevis. We control topography using fabricated micropost arrays (MPAs) and investigate the collective 3D migration of these multi-cellular systems in these MPAs. We find that the topography regulates both collective and individual cell migration and that dense MPAs reduce but do not eliminate tissue spreading. By modulating cell size through the cell cycle inhibitor Mitomycin C or the spacing of the MPAs we uncover how 3D topographical cues disrupt collective cell migration. We find surface topography can direct both single cell motility and tissue spreading, altering tissue-scale processes that enable efficient conversion of single cell motility into collective movement. Copyright © 2015 Elsevier Ltd. All rights reserved.

Auger spectroscopy of fracture surfaces of ceramics

NASA Technical Reports Server (NTRS)

Marcus, H. L.; Harris, J. M.; Szalkowski, F. J.

1974-01-01

Results of Auger electron spectroscopy (AES) studies of fracture surfaces in a series of ceramic materials, including Al2O3, MgO, and Si3N4, which were formed using different processing techniques. AES on the fractured surface of a lunar sample is also discussed. Scanning electron micrograph fractography is used to relate the surface chemistry to the failure mode. Combined argon ion sputtering and AES studies demonstrate the local variations in chemistry near the fracture surface. The problems associated with doing AES in insulators are also discussed, and the experimental techniques directed toward solving them are described.

Bond strength of novel CAD/CAM restorative materials to self-adhesive resin cement: the effect of surface treatments.

PubMed

Elsaka, Shaymaa E

2014-12-01

To evaluate the effect of different surface treatments on the microtensile bond strength (μTBS) of novel CAD/CAM restorative materials to self-adhesive resin cement. Two types of CAD/CAM restorative materials (Vita Enamic [VE] and Lava Ultimate [LU]) were used. The specimens were divided into five groups in each test according to the surface treatment performed; Gr 1 (control; no treatment), Gr 2 (sandblasted [SB]), Gr 3 (SB+silane [S]), Gr 4 (hydrofluoric acid [HF]), and Gr 5 (HF+S). A dual-curing self-adhesive resin cement (Bifix SE [BF]) was applied to each group for testing the adhesion after 24 h of storage in distilled water or after 30 days using the μTBS test. Following fracture testing, specimens were examined with a stereomicroscope and SEM. Surface roughness and morphology of the CAD/CAM restorative materials were characterized after treatment. Data were analyzed using ANOVA and Tukey's test. The surface treatment, type of CAD/CAM restorative material, and water storage periods showed a significant effect on the μTBS (p<0.001). For the LU/BF system, there was no significant difference in the bond strength values between different surface treatments (p>0.05). On the other hand, for the VE/BF system, surface treatment with HF+S showed higher bond strength values compared with SB and HF surface treatments (p<0.05). Surface roughness and SEM analyses showed that the surface topography of CAD/CAM restorative materials was modified after treatments. The effect of surface treatments on the bond strength of novel CAD/CAM restorative materials to resin cement is material dependent. The VE/BF CAD/CAM material provided higher bond strength values compared with the LU/BF CAD/CAM material.

Impact of lithosphere rheology on the dynamic topography

NASA Astrophysics Data System (ADS)

Burov, Evgueni; Gerya, Taras; Koptev, Alexander

2014-05-01

Dynamic topography is a key observable signature of the Earth's and planetary (e.g. Venus) mantle dynamics. In general view, it reflects complex mantle flow patterns, and hence is supposed to correlate at different extent with seismic tomography, SKS fast orientations, geodetic velocity fields and geoid anomalies. However, identification of dynamic topography had no systematic success, specifically in the Earth's continents. Here we argue that lithosphere rheology, in particular, rheological stratification of continents, results in modulation of dynamic topography, converting commonly expected long-wavelength/small amplitude undulations into short-wavelength surface undulations with wide amplitude spectrum, superimposed onto "tectonic" topography. These ideas are explored in 3D using unprecedentedly high resolution numerical experiments (grid step size 2-3 km for 1500x1500x600 km computational area) incorporating realistic rheologically stratified lithosphere. Such high resolution is actually needed to resolve small-scale crustal faulting and inter-layer coupling/uncoupling that shape surface topography. The results reveal strikingly discordant, counterintuitive features of 3D dynamic topography, going far beyond the inferences from previous models. In particular, even weak anisotropic tectonic stress field results both in large-scale small-amplitude dynamic topography and in strongly anisotropic short-wavelength (at least in one direction) dynamic topography with wide amplitude range (from 100 to 2000-3000 m), including basins and ranges and large-scale linear normal and strike-slip faults. Even very slightly pre-stressed strong lithosphere yields and localizes deformation much easier , than un-prestressed one, in response to plume impact and mantle flow. The results shed new light on the importance of lithosphere rheology and active role of lithosphere in mantle-lithosphere interactions as well as on the role of mantle flow and far-field stresses in tectonic-scale deformation. We show, for example, that crustal fault patterns initiated by plume impact are rapidly re-organized in sub-linear rifts and spreading centers, which orientation is largely dictated (e.g., perpendicular to) by the direction of the tectonic far-field stress field, as well as the plume-head material soon starts to flow along the sub-linear rifted shear zones in crustal and mantle lithosphere further amplifying their development. The final surface deformation and mantle flow patterns rapidly loose the initial axisymmetric character and take elongated sub-linear shapes whereas brittle deformation at surface is amplified and stabilized by coherent flow of mantle/plume-head material from below. These "tectonically" looking dynamic topography patterns are quite different from those expected from conventional models as well as from those directly observed, for example, on Venus where plume-lithosphere interactions produce only axisymmetric coronae domal-shaped features with radiating extensional rifts, suggesting that the Venusian lithosphere is rheologically too weak , and its crust is too thin, to produce any significant impact on the dynamic topography.

Eocene to mid-Pliocene landscape evolution in Scandinavia inferred from offshore sediment volumes and pre-glacial topography using inverse modelling

NASA Astrophysics Data System (ADS)

Pedersen, Vivi K.; Braun, Jean; Huismans, Ritske S.

2018-02-01

The origin of high topography in Scandinavia is highly debated, both in terms of its age and the underlying mechanism for its formation. Traditionally, the current high topography is assumed to have formed by several Cenozoic (mainly Neogene) phases of surface uplift and dissection of an old peneplain surface. These same surface uplift events are suggested to explain the increased deposition observed in adjacent offshore basins on the Norwegian shelf and in the North Sea. However, more recently it has been suggested that erosion and isostatic rock uplift of existing topography may also explain the recent evolution of topography in Scandinavia. For this latter view, the increased sedimentation towards the present is assumed to be a consequence of a climate related increase in erosion. In this study we explore whether inverse modelling of landscape evolution can give new insight into Eocene to mid-Pliocene (54-4 Ma) landscape evolution in the Scandinavian region. We do this by combining a highly efficient forward-in-time landscape evolution model (FastScape) with an optimization scheme suitable for non-linear inverse problems (the neighbourhood algorithm - NA). To limit our approach to the fluvial regime, we exclude the most recent mid-Pliocene-Quaternary time period where glacial erosion processes are expected to dominate landscape evolution. The "goodness" of our landscape evolution models is evaluated using i) sediment fluxes based on decompacted offshore sediment volumes and ii) maximum pre-glacial topography from a mid-Pliocene landscape, reconstructed using geophysical relief and offshore sediment volumes from the mid-Pliocene-Quaternary. We find several tested scenarios consistent with the offshore sediment record and the maximum elevation for our reconstructed pre-glacial (mid-Pliocene) landscape reconstruction, including: I) substantial initial topography ( 2 km) at 54 Ma and no induced tectonic rock uplift, II) the combination of some initial topography ( 1.1 km) at 54 Ma and minor continued rock uplift (< 0.04 mm/yr) until 4 Ma, and III) a two-phased tectonic rock uplift of an initially low topography ( 0.1 km). However, out of these, only scenario I (no tectonic rock uplift) matches large-scale characteristics of our reconstructed pre-glacial (mid-Pliocene) topography well. Our preferred model for Eocene to mid-Pliocene landscape evolution in Scandinavia is therefore one where high topography ( 2 km) has existed throughout the time interval from 54 to 4 Ma. We do not find several phases of peneplain surface uplift necessary to explain offshore sediment volumes and large-scale topographic patterns. On the contrary, extensive peneplain dissection seems inconsistent with the low rates of erosion we infer based on the offshore sediment volumes.

Dynamic sea surface topography, gravity and improved orbit accuracies from the direct evaluation of SEASAT altimeter data

NASA Technical Reports Server (NTRS)

Marsh, J. G.; Lerch, F.; Koblinsky, C. J.; Klosko, S. M.; Robbins, J. W.; Williamson, R. G.; Patel, G. B.

1989-01-01

A method for the simultaneous solution of dynamic ocean topography, gravity and orbits using satellite altimeter data is described. A GEM-T1 based gravitational model called PGS-3337 that incorporates Seasat altimetry, surface gravimetry and satellite tracking data has been determined complete to degree and order 50. The altimeter data is utilized as a dynamic observation of the satellite's height above the sea surface with a degree 10 model of dynamic topography being recovered simultaneously with the orbit parameters, gravity and tidal terms in this model. PGS-3337 has a geoid uncertainty of 60 cm root-mean-square (RMS) globally, with the uncertainty over the altimeter tracked ocean being in the 25 cm range. Doppler determined orbits for Seasat, show large improvements, with the sub-30 cm radial accuracies being achieved. When altimeter data is used in orbit determination, radial orbital accuracies of 20 cm are achieved. The RMS of fit to the altimeter data directly gives 30 cm fits for Seasat when using PGS-3337 and its geoid and dynamic topography model. This performance level is two to three times better than that achieved with earlier Goddard earth models (GEM) using the dynamic topography from long-term oceanographic averages. The recovered dynamic topography reveals the global long wavelength circulation of the oceans with a resolution of 1500 km. The power in the dynamic topography recovery is now found to be closer to that of oceanographic studies than for previous satellite solutions. This is attributed primarily to the improved modeling of the geoid which has occurred. Study of the altimeter residuals reveals regions where tidal models are poor and sea state effects are major limitations.

A Generalized Subsurface Flow Parameterization Considering Subgrid Spatial Variability of Recharge and Topography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Maoyi; Liang, Xu; Leung, Lai R.

2008-12-05

Subsurface flow is an important hydrologic process and a key component of the water budget, especially in humid regions. In this study, a new subsurface flow formulation is developed that incorporates spatial variability of both topography and recharge. It is shown through theoretical derivation and case studies that the power law and exponential subsurface flow parameterizations and the parameterization proposed by Woods et al.[1997] are all special cases of the new formulation. The subsurface flows calculated using the new formulation compare well with values derived from observations at the Tulpehocken Creek and Walnut Creek watersheds. Sensitivity studies show that whenmore » the spatial variability of topography or recharge, or both is increased, the subsurface flows increase at the two aforementioned sites and the Maimai hillslope. This is likely due to enhancement of interactions between the groundwater table and the land surface that reduce the flow path. An important conclusion of this study is that the spatial variability of recharge alone, and/or in combination with the spatial variability of topography can substantially alter the behaviors of subsurface flows. This suggests that in macroscale hydrologic models or land surface models, subgrid variations of recharge and topography can make significant contributions to the grid mean subsurface flow and must be accounted for in regions with large surface heterogeneity. This is particularly true for regions with humid climate and relatively shallow groundwater table where the combined impacts of spatial variability of recharge and topography are shown to be more important. For regions with arid climate and relatively deep groundwater table, simpler formulations, especially the power law, for subsurface flow can work well, and the impacts of subgrid variations of recharge and topography may be ignored.« less

Effects of Polishing Bur Application Force and Reuse on Sintered Zirconia Surface Topography.

PubMed

Fischer, N G; Tsujimoto, A; Baruth, A G

2018-03-16

Limited information is available on how to polish and finish zirconia surfaces following computer-aided design/computer-aided manufacturing (CAD/CAM), specifically, how differing application forces and reuse of zirconia polishing systems affect zirconia topography. To determine the effect of differing, clinically relevant, polishing application forces and multiple usages of polishing burs on the surface topography of CAD/CAM zirconia. One hundred twenty 220-grit carbide finished zirconia disks were sintered according to manufacturer's directions and divided into two groups for the study of two coarse polishing bur types. Each group was divided into subgroups for polishing (15,000 rpm) at 15 seconds for 1.0 N, 4.5 N, or 11 N of force using a purpose-built fixture. Subgroups were further divided to study the effects of polishing for the first, fifth, 15th, and 30th bur use, simulating clinical procedures. Unpolished surfaces served as a control group. Surfaces were imaged with noncontact optical profilometry (OP) and atomic force microscopy (AFM) to measure average roughness values (Ra). Polishing burs were optically examined for wear. Scanning electron microscopy (SEM) was performed on burs and zirconia surfaces. One-way ANOVA with post hoc Tukey HSD (honest significant difference) tests (α=0.05) were used for statistical analyses. AFM and OP Ra values of all polished surfaces were significantly lower than those of the unpolished control. Different polishing forces and bur reuse showed no significant differences in AFM Ra. However, significant differences in OP Ra were found due to differing application forces and bur reuse between the first and subsequent uses. SEM and optical micrographs revealed notable bur wear, increasing with increasing reuse. SEM and AFM micrographs clearly showed polished, periodic zirconia surfaces. Nanoscale topography, as analyzed with kurtosis and average groove depth, was found dependent on the specific polishing bur type. These in vitro results suggest changes in OP Ra due to bur reuse and polishing application force. Within the parameters of this study, the resultant topography of zirconia polishing is force-dependent and the reuse of coarse polishing burs is possible without statistically significant differences in Ra values after initial use. Nanoscale and microscale topography were shown to depend on specific polishing bur type.

Stress distribution and topography of Tellus Regio, Venus

NASA Technical Reports Server (NTRS)

Williams, David R.; Greeley, Ronald

1989-01-01

The Tellus Regio area of Venus represents a subset of a narrow latitude band where Pioneer Venus Orbiter (PVO) altimetry data, line-of-sight (LOS) gravity data, and Venera 15/16 radar images have all been obtained with good resolution. Tellus Regio also has a wide variety of surface morphologic features, elevations ranging up to 2.5 km, and a relatively low LOS gravity anomaly. This area was therefore chosen in order to examine the theoretical stress distributions resulting from various models of compensation of the observed topography. These surface stress distributions are then compared with the surface morphology revealed in the Venera 15/16 radar images. Conclusions drawn from these comparisons will enable constraints to be put on various tectonic parameters relevant to Tellus Regio. The stress distribution is calculated as a function of the topography, the equipotential anomaly, and the assumed model parameters. The topography data is obtained from the PVO altimetry. The equipotential anomaly is estimated from the PVO LOS gravity data. The PVO LOS gravity represents the spacecraft accelerations due to mass anomalies within the planet. These accelerations are measured at various altitudes and angles to the local vertical and therefore do not lend themselves to a straightforward conversion. A minimum variance estimator of the LOS gravity data is calculated, taking into account the various spacecraft altitudes and LOS angles and using the measured PVO topography as an a priori constraint. This results in an estimated equivalent surface mass distribution, from which the equipotential anomaly is determined.

Simulation of extreme rainfall event of November 2009 over Jeddah, Saudi Arabia: the explicit role of topography and surface heating

NASA Astrophysics Data System (ADS)

Almazroui, Mansour; Raju, P. V. S.; Yusef, A.; Hussein, M. A. A.; Omar, M.

2018-04-01

In this paper, a nonhydrostatic Weather Research and Forecasting (WRF) model has been used to simulate the extreme precipitation event of 25 November 2009, over Jeddah, Saudi Arabia. The model is integrated in three nested (27, 9, and 3 km) domains with the initial and boundary forcing derived from the NCEP reanalysis datasets. As a control experiment, the model integrated for 48 h initiated at 0000 UTC on 24 November 2009. The simulated rainfall in the control experiment depicts in well agreement with Tropical Rainfall Measurement Mission rainfall estimates in terms of intensity as well as spatio-temporal distribution. Results indicate that a strong low-level (850 hPa) wind over Jeddah and surrounding regions enhanced the moisture and temperature gradient and created a conditionally unstable atmosphere that favored the development of the mesoscale system. The influences of topography and heat exchange process in the atmosphere were investigated on the development of extreme precipitation event; two sensitivity experiments are carried out: one without topography and another without exchange of surface heating to the atmosphere. The results depict that both surface heating and topography played crucial role in determining the spatial distribution and intensity of the extreme rainfall over Jeddah. The topography favored enhanced uplift motion that further strengthened the low-level jet and hence the rainfall over Jeddah and adjacent areas. On the other hand, the absence of surface heating considerably reduced the simulated rainfall by 30% as compared to the observations.

Biological evaluation of ultrananocrystalline and nanocrystalline diamond coatings.

PubMed

Skoog, Shelby A; Kumar, Girish; Zheng, Jiwen; Sumant, Anirudha V; Goering, Peter L; Narayan, Roger J

2016-12-01

Nanostructured biomaterials have been investigated for achieving desirable tissue-material interactions in medical implants. Ultrananocrystalline diamond (UNCD) and nanocrystalline diamond (NCD) coatings are the two most studied classes of synthetic diamond coatings; these materials are grown using chemical vapor deposition and are classified based on their nanostructure, grain size, and sp 3 content. UNCD and NCD are mechanically robust, chemically inert, biocompatible, and wear resistant, making them ideal implant coatings. UNCD and NCD have been recently investigated for ophthalmic, cardiovascular, dental, and orthopaedic device applications. The aim of this study was (a) to evaluate the in vitro biocompatibility of UNCD and NCD coatings and (b) to determine if variations in surface topography and sp 3 content affect cellular response. Diamond coatings with various nanoscale topographies (grain sizes 5-400 nm) were deposited on silicon substrates using microwave plasma chemical vapor deposition. Scanning electron microscopy and atomic force microscopy revealed uniform coatings with different scales of surface topography; Raman spectroscopy confirmed the presence of carbon bonding typical of diamond coatings. Cell viability, proliferation, and morphology responses of human bone marrow-derived mesenchymal stem cells (hBMSCs) to UNCD and NCD surfaces were evaluated. The hBMSCs on UNCD and NCD coatings exhibited similar cell viability, proliferation, and morphology as those on the control material, tissue culture polystyrene. No significant differences in cellular response were observed on UNCD and NCD coatings with different nanoscale topographies. Our data shows that both UNCD and NCD coatings demonstrate in vitro biocompatibility irrespective of surface topography.

Controlling flows in microchannels with patterned surface charge and topography.

PubMed

Stroock, Abraham D; Whitesides, George M

2003-08-01

This Account reviews two procedures for controlling the flow of fluids in microchannels. The first procedure involves patterning the density of charge on the inner surfaces of a channel. These patterns generate recirculating electroosmotic flows in the presence of a steady electric field. The second procedure involves patterning topography on an inner surface of a channel. These patterns generate recirculation in the cross-section of steady, pressure-driven flows. This Account summarizes applications of these flow to mixing and to controlling dispersion (band broadening).

Correcting for surface topography in X-ray fluorescence imaging

PubMed Central

Geil, E. C.; Thorne, R. E.

2014-01-01

Samples with non-planar surfaces present challenges for X-ray fluorescence imaging analysis. Here, approximations are derived to describe the modulation of fluorescence signals by surface angles and topography, and suggestions are made for reducing this effect. A correction procedure is developed that is effective for trace element analysis of samples having a uniform matrix, and requires only a fluorescence map from a single detector. This procedure is applied to fluorescence maps from an incised gypsum tablet. PMID:25343805

Enhanced Arctic Mean Sea Surface and Mean Dynamic Topography including retracked CryoSat-2 Data

NASA Astrophysics Data System (ADS)

Andersen, O. B.; Jain, M.; Stenseng, L.; Knudsen, P.

2014-12-01

A reliable mean sea surface (MSS) is essential to derive a good mean dynamic topography (MDT) and for the estimation of short and long-term changes in the sea surface. The lack of satellite radar altimetry observations above 82 degrees latitude means that existing mean sea surface models have been unreliable in the Arctic Ocean. We here present the latest DTU mean sea surface and mean dynamic topography models combining conventional altimetry with retracked CryoSat-2 data to improve the reliability in the Arctic Ocean. For the derivation of a mean dynamic topography the ESA GOCE derived geoid model have been used to constrain the longer wavelength. We present the retracking of C2 SAR data using various retrackes and how we have been able to combine data from various retrackers under various sea ice conditions. DTU13MSS and DTU13MDT are the newest state of the art global high-resolution models including CryoSat-2 data to extend the satellite radar altimetry coverage up to 88 degrees latitude and through combination with a GOCE geoid model completes coverage all the way to the North Pole. Furthermore the SAR and SARin capability of CryoSat-2 dramatically increases the amount of useable sea surface returns in sea-ice covered areas compared to conventional radar altimeters like ENVISAT and ERS-1/2. With the inclusion of CryoSat-2 data the new mean sea surface is improved by more than 20 cm above 82 degrees latitude compared with the previous generation of mean sea surfaces.

Surface interactions, thermodynamics and topography of binary monolayers of Insulin with dipalmitoylphosphatidylcholine and 1-palmitoyl-2-oleoylphosphatidylcholine at the air/water interface.

PubMed

Grasso, E J; Oliveira, R G; Maggio, B

2016-02-15

The molecular packing, thermodynamics and surface topography of binary Langmuir monolayers of Insulin and DPPC (dipalmitoylphosphatidylcholine) or POCP (1-palmitoyl-2-oleoylphosphatidylcholine) at the air/water interface on Zn(2+) containing solutions were studied. Miscibility and interactions were ascertained by the variation of surface pressure-mean molecular area isotherms, surface compressional modulus and surface (dipole) potential with the film composition. Brewster Angle Microscopy was used to visualize the surface topography of the monolayers. Below 20mN/m Insulin forms stable homogenous films with DPPC and POPC at all mole fractions studied (except for films with XINS=0.05 at 10mN/m where domain coexistence was observed). Above 20mN/m, a segregation process between mixed phases occurred in all monolayers without squeezing out of individual components. Under compression the films exhibit formation of a viscoelastic or kinetically trapped organization leading to considerable composition-dependent hysteresis under expansion that occurs with entropic-enthalpic compensation. The spontaneously unfavorable interactions of Insulin with DPPC are driven by favorable enthalpy that is overcome by unfavorable entropic ordering; in films with POPC both the enthalpic and entropic effects are unfavorable. The surface topography reveals domain coexistence at relatively high pressure showing a striped appearance. The interactions of Insulin with two major membrane phospholipids induces composition-dependent and long-range changes of the surface organization that ought to be considered in the context of the information-transducing capabilities of the hormone for cell functioning. Copyright © 2015 Elsevier Inc. All rights reserved.

Technical and Regulatory Guidance for In Situ Chemical Oxidation of Contaminated Soil and Groundwater Second Edition

DTIC Science & Technology

2005-01-01

PA Ozone (full scale) Silty sand underlain by fractured schist and shale Petroleum hydrocarbons Former Wood Treatment Site, Sonoma County , CA...Wood Treatment Site, Sonoma County , California Contaminant: Pentachlorophenol and creosote (i.e., PAHs) Oxidant: Ozone Regulatory Agency Contact...topography is essentially flat and paved, and the facility is located on northern Sonoma County , California. The site subsurface consists of very

Ocean bottom characterestics between Iles Rodrigues and Chagos-Maldives Archepelago in western Indian Ocean

NASA Astrophysics Data System (ADS)

Longhinos, Biju; Thanu Iyer, Radhakrishnan; Mohan, Karthika

2014-05-01

The geological and geophysical complexities in Indian ocean basin, pointed out by many earlier workers remained unresolved. Instead, taking aid from stop gap arguments, the data has been construed to follow plate tectonics format. The concept of large igneous complexes emplaced through crustal drifting ( between the India and Mozambique) during later Mesozoic to Recent fail to address geophysical characteristics exhibited here. The geophysical signatures of the sub crustal part of the ocean here resemble to that of continental regions elsewhere. Granites, greenstones and mylonized gabbro, recovered from the western Indian ocean basin, rather give Late Pre- Cambrian and Paleozoic isotopic dates. Under this light, the present paper looks into the ocean bottom characteristics of a region between iles Rodrigues and Chagos- Maldives archipelago. The region has first order curvilienar fractures, with along which the crust has displaced more than 1000m. The sea-bottom topography of the region has been modeled in Geographical Information System environment using Modified ETOPO5 provided by National Institute of Oceanography. The spatial relationship of topography with gravity and magnetic data area are analysed visually and mathematically. The detail bathymetry, gravity and magnetic data give morphology similar to that of half graben formed on a felsic crust, which later has undergone basification / eclogitization through first order fracture zones.

Fracture sealing caused by mineral precipitation: The role of aperture and mineral heterogeneity on precipitation-induced permeability loss

NASA Astrophysics Data System (ADS)

Jones, T.; Detwiler, R. L.

2017-12-01

Fractures act as dominant pathways for fluid flow in low-permeability rocks. However, in many subsurface environments, fluid rock reactions can lead to mineral precipitation, which alters fracture surface geometry and reduces fracture permeability. In natural fractures, surface mineralogy and roughness are often heterogeneous, leading to variations in both velocity and reactive surface area. The combined effects of surface roughness and mineral heterogeneity can lead to large disparities in local precipitation rates that are difficult to predict due to the strong coupling between dissolved mineral transport and reactions at the fracture surface. Recent experimental observations suggest that mineral precipitation in a heterogeneous fracture may promote preferential flow and focus large dissolved ion concentrations into regions with limited reactive surface area. Here, we build on these observations using reactive transport simulations. Reactive transport is simulated with a quasi-steady-state 2D model that uses a depth-averaged mass-transfer relationship to describe dissolved mineral transport across the fracture aperture and local precipitation reactions. Mineral precipitation-induced changes to fracture surface geometry are accounted for using two different approaches: (1) by only allowing reactive minerals to grow vertically, and (2) by allowing three-dimensional mineral growth at reaction sites. Preliminary results from simulations using (1) suggest that precipitation-induced aperture reduction focuses flow into thin flow paths. This flow focusing causes a reduction in the fracture-scale precipitation rate, and precipitation ceases when the reaction zone extends the entire length of the fracture. This approach reproduces experimental observations at early time reasonably well, but as precipitation proceeds, reaction sites can grow laterally along the fracture surfaces, which is not predicted by (1). To account for three-dimensional mineral growth (2), we have incorporated a level-set-method based approach for tracking the mineral interfaces in three dimensions. This provides a mechanistic approach for simulating the dynamics of the formation, and eventual closing, of preferential flow paths by precipitation-induced aperture alteration, that do not occur using (1).

Ultrasonic probing of the fracture process zone in rock using surface waves

NASA Technical Reports Server (NTRS)

Swanson, P. L.; Spetzler, H.

1984-01-01

A microcrack process zone is frequently suggested to accompany macrofractures in rock and play an important role in the resistance to fracture propagation. Attenuation of surface waves propagating through mode I fractures in wedge-loaded double-cantilever beam specimens of Westerly granite has been recorded in an attempt to characterize the structure of the fracture process zone. The ultrasonic measurements do not support the generally accepted model of a macroscopic fracture that incrementally propagates with the accompaniment of a cloud of microcracks. Instead, fractures in Westerly granite appear to form as gradually separating surfaces within a zone having a width of a few millimeters and a length of several tens of millimeters. A fracture process zone of this size would necessitate the use of meter-sized specimens in order for linear elastic fracture mechanics to be applicable.

Engineering a Biocompatible Scaffold with Either Micrometre or Nanometre Scale Surface Topography for Promoting Protein Adsorption and Cellular Response

PubMed Central

Le, Xuan; Poinern, Gérrard Eddy Jai; Ali, Nurshahidah; Berry, Cassandra M.; Fawcett, Derek

2013-01-01

Surface topographical features on biomaterials, both at the submicrometre and nanometre scales, are known to influence the physicochemical interactions between biological processes involving proteins and cells. The nanometre-structured surface features tend to resemble the extracellular matrix, the natural environment in which cells live, communicate, and work together. It is believed that by engineering a well-defined nanometre scale surface topography, it should be possible to induce appropriate surface signals that can be used to manipulate cell function in a similar manner to the extracellular matrix. Therefore, there is a need to investigate, understand, and ultimately have the ability to produce tailor-made nanometre scale surface topographies with suitable surface chemistry to promote favourable biological interactions similar to those of the extracellular matrix. Recent advances in nanoscience and nanotechnology have produced many new nanomaterials and numerous manufacturing techniques that have the potential to significantly improve several fields such as biological sensing, cell culture technology, surgical implants, and medical devices. For these fields to progress, there is a definite need to develop a detailed understanding of the interaction between biological systems and fabricated surface structures at both the micrometre and nanometre scales. PMID:23533416

Fluid surface compensation in digital holographic microscopy for topography measurement

NASA Astrophysics Data System (ADS)

Lin, Li-Chien; Tu, Han-Yen; Lai, Xin-Ji; Wang, Sheng-Shiun; Cheng, Chau-Jern

2012-06-01

A novel technique is presented for surface compensation and topography measurement of a specimen in fluid medium by digital holographic microscopy (DHM). In the measurement, the specimen is preserved in a culture dish full of liquid culture medium and an environmental vibration induces a series of ripples to create a non-uniform background on the reconstructed phase image. A background surface compensation algorithm is proposed to account for this problem. First, we distinguish the cell image from the non-uniform background and a morphological image operation is used to reduce the noise effect on the background surface areas. Then, an adaptive sampling from the background surface is employed, taking dense samples from the high-variation area while leaving the smooth region mostly untouched. A surface fitting algorithm based on the optimal bi-cubic functional approximation is used to establish a whole background surface for the phase image. Once the background surface is found, the background compensated phase can be obtained by subtracting the estimated background from the original phase image. From the experimental results, the proposed algorithm performs effectively in removing the non-uniform background of the phase image and has the ability to obtain the specimen topography inside fluid medium under environmental vibrations.

A normalisation framework for (hyper-)spectral imagery

NASA Astrophysics Data System (ADS)

Grumpe, Arne; Zirin, Vladimir; Wöhler, Christian

2015-06-01

It is well known that the topography has an influence on the observed reflectance spectra. This influence is not compensated by spectral ratios, i.e. the effect is wavelength dependent. In this work, we present a complete normalisation framework. The surface temperature is estimated based on the measured surface reflectance. To normalise the spectral reflectance with respect to a standard illumination geometry, spatially varying reflectance parameters are estimated based on a non-linear reflectance model. The reflectance parameter estimation has one free parameter, i.e. a low-pass function, which sets the scale of the spatial-variance, i.e. the lateral resolution of the reflectance parameter maps. Since the local surface topography has a major influence on the measured reflectance, often neglected shading information is extracted from the spectral imagery and an existing topography model is refined to image resolution. All methods are demonstrated on the Moon Mineralogy Mapper dataset. Additionally, two empirical methods are introduced that deal with observed systematic reflectance changes in co-registered images acquired at different phase angles. These effects, however, may also be caused by the sensor temperature, due to its correlation with the phase angle. Surface temperatures above 300 K are detected and are very similar to a reference method. The proposed method, however, seems more robust in case of absorptions visible in the reflectance spectrum near 2000 nm. By introducing a low-pass into the computation of the reflectance parameters, the reflectance behaviour of the surfaces may be derived at different scales. This allows for an iterative refinement of the local surface topography using shape from shading and the computation reflectance parameters. The inferred parameters are derived from all available co-registered images and do not show significant influence of the local surface topography. The results of the empirical correction show that both proposed methods greatly reduce the influence of different phase angles or sensor temperatures.

Tribology of bio-inspired nanowrinkled films on ultrasoft substrates.

PubMed

Lackner, Juergen M; Waldhauser, Wolfgang; Major, Lukasz; Teichert, Christian; Hartmann, Paul

2013-01-01

Biomimetic design of new materials uses nature as antetype, learning from billions of years of evolution. This work emphasizes the mechanical and tribological properties of skin, combining both hardness and wear resistance of its surface (the stratum corneum) with high elasticity of the bulk (epidermis, dermis, hypodermis). The key for combination of such opposite properties is wrinkling, being consequence of intrinsic stresses in the bulk (soft tissue): Tribological contact to counterparts below the stress threshold for tissue trauma occurs on the thick hard stratum corneum layer pads, while tensile loads smooth out wrinkles in between these pads. Similar mechanism offers high tribological resistance to hard films on soft, flexible polymers, which is shown for diamond-like carbon (DLC) and titanium nitride thin films on ultrasoft polyurethane and harder polycarbonate substrates. The choice of these two compared substrate materials will show that ultra-soft substrate materials are decisive for the distinct tribological material. Hierarchical wrinkled structures of films on these substrates are due to high intrinsic compressive stress, which evolves during high energetic film growth. Incremental relaxation of these stresses occurs by compound deformation of film and elastic substrate surface, appearing in hierarchical nano-wrinkles. Nano-wrinkled topographies enable high elastic deformability of thin hard films, while overstressing results in zigzag film fracture along larger hierarchical wrinkle structures. Tribologically, these fracture mechanisms are highly important for ploughing and sliding of sharp and flat counterparts on hard-coated ultra-soft substrates like polyurethane. Concentration of polyurethane deformation under the applied normal loads occurs below these zigzag cracks. Unloading closes these cracks again. Even cyclic testing do not lead to film delamination and retain low friction behavior, if the adhesion to the substrate is high and the initial friction coefficient of the film against the sliding counterpart low, e.g. found for DLC.

Landscape evolution on Mars - A model of aeolian denudation in Gale Crater

NASA Astrophysics Data System (ADS)

Day, M. D.; Kocurek, G.; Grotzinger, J. P.

2015-12-01

Aeolian erosion has been the dominant geomorphic agent to shape the surface of Mars for the past ~3.5 billion years. Although individual geomorphic features evidencing aeolian activity are well understood (e.g., yardangs, dune fields, and wind streaks), landscapes formed by aeolian erosion remain poorly characterized. Intra-crater sedimentary mounds are hypothesized to have formed by wind deflation of craters once filled with flat-lying strata, and, therefore, should be surrounded by landscapes formed by aeolian erosion. Here we present a landscape evolution model that provides both an initial characterization of aeolian landscapes, and a mechanism for large-scale excavation. Wind excavation of Gale Crater to form the 5 km high Mount Sharp would require removal of 6.4 x 104 km3 of sediment. Imagery in Gale Crater from satellites and the Mars Science Laboratory rover Curiosity shows a surface characterized by first-cycle aeolian erosion of bedrock. The overall landscape is interpreted to represent stages in a cycle of aeolian deflation and excavation, enhanced by physical weathering (e.g., thermal fracturing, cratering). Initial wind erosion of bedrock is enhanced along fractures, producing retreating scarps. Underlying less resistant layers then erode faster than the armoring cap rock, increasing relief in scarps to form retreating mesas. As scarp retreat continues, boulders from the armoring cap unit break away and cover the hillslopes of less resistant material below the scarps. Eventually all material from the capping unit is eroded away and a boulder-capped hill remains. Winnowing of fine material flattens hillslope topography, leaving behind a desert pavement. Over long enough time, this pavement is breached and the cycle begins anew. This cycle of landscape denudation by the wind is similar to that of water, but lacks characteristic subaqueous features such as dendritic drainage networks.

Soil-Water Balance (SWB) model estimates of soil-moisture variability and groundwater recharge in the South Platte watershed, Colorado

NASA Astrophysics Data System (ADS)

Anderson, A. M.; Walker, E. L.; Hogue, T. S.; Ruybal, C. J.

2015-12-01

Unconventional energy production in semi-arid regions places additional stress on already over-allocated water systems. Production of shale gas and oil resources in northern Colorado has rapidly increased since 2010, and is expected to continue growing due to advances in horizontal drilling and hydraulic fracturing. This unconventional energy production has implications for the availability of water in the South Platte watershed, where water demand for hydraulic fracturing of unconventional shale resources reached ~16,000 acre-feet in 2014. Groundwater resources are often exploited to meet water demands for unconventional energy production in regions like the South Platte basin, where surface water supply is limited and allocated across multiple uses. Since groundwater is often a supplement to surface water in times of drought and peak demand, variability in modeled recharge estimates can significantly impact projected availability. In the current work we used the Soil-Water Balance Model (SWB) to assess the variability in model estimates of actual evapotranspiration (ET) and soil-moisture conditions utilized to derive estimates of groundwater recharge. Using both point source and spatially distributed data, we compared modeled actual ET and soil-moisture derived from several potential ET methods, such as Thornthwaite-Mather, Jense-Haise, Turc, and Hargreaves-Samani, to historic soil moisture conditions obtained through sources including the Gravity Recovery and Climate Experiment (GRACE). In addition to a basin-scale analysis, we divided the South Platte watershed into sub-basins according to land cover to evaluate model capabilities of estimating soil-moisture parameters with variations in land cover and topography. Results ultimately allow improved prediction of groundwater recharge under future scenarios of climate and land cover change. This work also contributes to complementary subsurface groundwater modeling and decision support modeling in the South Platte.

Tribology of bio-inspired nanowrinkled films on ultrasoft substrates

PubMed Central

Lackner, Juergen M.; Waldhauser, Wolfgang; Major, Lukasz; Teichert, Christian; Hartmann, Paul

2013-01-01

Biomimetic design of new materials uses nature as antetype, learning from billions of years of evolution. This work emphasizes the mechanical and tribological properties of skin, combining both hardness and wear resistance of its surface (the stratum corneum) with high elasticity of the bulk (epidermis, dermis, hypodermis). The key for combination of such opposite properties is wrinkling, being consequence of intrinsic stresses in the bulk (soft tissue): Tribological contact to counterparts below the stress threshold for tissue trauma occurs on the thick hard stratum corneum layer pads, while tensile loads smooth out wrinkles in between these pads. Similar mechanism offers high tribological resistance to hard films on soft, flexible polymers, which is shown for diamond-like carbon (DLC) and titanium nitride thin films on ultrasoft polyurethane and harder polycarbonate substrates. The choice of these two compared substrate materials will show that ultra-soft substrate materials are decisive for the distinct tribological material. Hierarchical wrinkled structures of films on these substrates are due to high intrinsic compressive stress, which evolves during high energetic film growth. Incremental relaxation of these stresses occurs by compound deformation of film and elastic substrate surface, appearing in hierarchical nano-wrinkles. Nano-wrinkled topographies enable high elastic deformability of thin hard films, while overstressing results in zigzag film fracture along larger hierarchical wrinkle structures. Tribologically, these fracture mechanisms are highly important for ploughing and sliding of sharp and flat counterparts on hard-coated ultra-soft substrates like polyurethane. Concentration of polyurethane deformation under the applied normal loads occurs below these zigzag cracks. Unloading closes these cracks again. Even cyclic testing do not lead to film delamination and retain low friction behavior, if the adhesion to the substrate is high and the initial friction coefficient of the film against the sliding counterpart low, e.g. found for DLC. PMID:24688710

Environmentally Assisted Cracking: Overview of Evidence for an Adsorption-Induced Localised-Slip Process,

DTIC Science & Technology

1986-12-01

Prior to examination of LME fractures, liquid or solid metals were removed from fracture surfaces as follows: Mercury was evaporated from fractures in a...1 mm/s. Under these conditions, the appearance of fracture surfaces was identical to that produced by rapid fracture (-1 mm/s) in liquid mercury ...Furthermore, the appearance of fractures depended somewhat on the orientation of crystals but was the same in hydrogen and mercury environments for each

Seafloor geomorphic manifestations of gas venting and shallow subbottom gas hydrate occurrences

USGS Publications Warehouse

Paull, C K; Caress, D W; Thomas, Hans; Lundsten, Eve M.; Anderson, Kayce; Gwiazda, Roberto; Riedel, M; McGann, Mary; Herguera, J C

2015-01-01

High-resolution multibeam bathymetry data collected with an autonomous underwater vehicle (AUV) complemented by compressed high-intensity radar pulse (Chirp) profiles and remotely operated vehicle (ROV) observations and sediment sampling reveal a distinctive rough topography associated with seafloor gas venting and/or near-subsurface gas hydrate accumulations. The surveys provide 1 m bathymetric grids of deep-water gas venting sites along the best-known gas venting areas along the Pacific margin of North America, which is an unprecedented level of resolution. Patches of conspicuously rough seafloor that are tens of meters to hundreds of meters across and occur on larger seafloor topographic highs characterize seepage areas. Some patches are composed of multiple depressions that range from 1 to 100 m in diameter and are commonly up to 10 m deeper than the adjacent seafloor. Elevated mounds with relief of >10 m and fractured surfaces suggest that seafloor expansion also occurs. Ground truth observations show that these areas contain broken pavements of methane-derived authigenic carbonates with intervening topographic lows. Patterns seen in Chirp profiles, ROV observations, and core data suggest that the rough topography is produced by a combination of diagenetic alteration, focused erosion, and inflation of the seafloor. This characteristic texture allows previously unknown gas venting areas to be identified within these surveys. A conceptual model for the evolution of these features suggests that these morphologies develop slowly over protracted periods of slow seepage and shows the impact of gas venting and gas hydrate development on the seafloor morphology.

Cement/caprock fracture healing experiments to assess the integrity of CO2 injection wells

NASA Astrophysics Data System (ADS)

Du Frane, W. L.; Mason, H. E.; Walsh, S. D.; Ruddle, D. G.; Carroll, S.

2012-12-01

It has been speculated that fractures along wellbore cement/caprock interfaces may provide a path for release of carbon from both long-term sequestration-sites and CO2-based enhanced oil recovery operations. The goal of this study is to evaluate the potential for fracture growth and healing in the wellbore environment, and its impact on wellbore permeability. A series of flow-through experiments was conducted, in which sample cores containing a planar fracture between impermeable caprock (compacted quartz, from 13,927' depth in Kern County) and cement (Portland G cured by ATSM standards) were reacted with brine containing variable amounts of carbonic acid (pCO2 between 0 and 3 MPa). The initial fracture geometry was controlled by grinding the caprock and cement pieces flat, and then bead blasting topography into the cement surfaces. Runs lasted 4-8 days with cores and brine maintained at constant temperature (60 °C). Constant confining pressure (24.8 MPa) was applied to cores, while brine was flowed with constant rates (0.05-0.10 mL/min) and pore pressure (12.4 MPa). Geomechanical and geochemical responses of the fractures were monitored by in situ measurements of differential pressure, and by periodically sampling output brine to analyze compositional changes. In every experiment the total permeability of samples cores decreased substantially. For runs using brine with pCO2 = 3 MPa, sample permeability continually decreased by over a factor of 200. Sample permeability also decreased by a factor of 50 having stabilized after ~3 days in a run using brine without CO2 (pCO2 = 0 MPa). These reductions in permeability appear to be the result of chemically-induced changes to the mechanical properties of the cement surface. Prior to reaction, the cement-caprock samples had high strength and elastic response to changes in stress during loading. After the experiments, the samples were weaker, and showed inelastic response to changes in stress during unloading. All cement surfaces exposed to CO2-rich brine were heavily reacted, as evidenced by coatings of rust-colored amorphous material. X-ray micro-tomography images revealed a series of reaction zones consistent with the results of related experiments by other researchers [e.g. Kutchko et al. 2007]. The mechanical properties of the individual reaction zones were evaluated by nano-indentation. Sampling during runs indicated that brine with pCO2 = 3 MPa became substantially enriched in Ca, Si, and Al, whereas composition of output brine with pCO2 = 0 MPa had little change over the run duration. The enrichment of Al in the brine with pCO2 = 3 MPa indicates that both Al -bearing minerals and amorphous calcium-silicate-hydrate (CSH) dissolved from the cement. Geochemical reaction pathways were further characterized in the reacted zones with the cement by scanning electron microscope, x-ray diffraction, and solid state NMR spectroscopy. These results suggest that the evolution of fractures in our experiments are determined by 3 competing factors: 1) swelling of CSH through hydration from the brine, 2) dissolution of cement into brine containing CO2, and 3) mechanical weakening of cement by chemical reaction with CO2. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48 and Contract DE-AC52-07NA27344.

Novel Zirconia Surface Treatments for Enhanced Osseointegration: Laboratory Characterization

PubMed Central

Ewais, Ola H.; Al Abbassy, Fayza; Ghoneim, Mona M.; Aboushelib, Moustafa N.

2014-01-01

Purpose. The aim of this study was to evaluate three novel surface treatments intended to improve osseointegration of zirconia implants: selective infiltration etching treatment (SIE), fusion sputtering (FS), and low pressure particle abrasion (LPPA). The effects of surface treatments on roughness, topography, hardness, and porosity of implants were also assessed. Materials and Methods. 45 zirconia discs (19 mm in diameter × 3 mm in thickness) received 3 different surface treatments: selective infiltration etching, low pressure particle abrasion with 30 µm alumina, and fusion sputtering while nontreated surface served as control. Surface roughness was evaluated quantitatively using profilometery, porosity was evaluated using mercury prosimetry, and Vickers microhardness was used to assess surface hardness. Surface topography was analyzed using scanning and atomic force microscopy (α = 0.05). Results. There were significant differences between all groups regarding surface roughness (F = 1678, P < 0.001), porosity (F = 3278, P < 0.001), and hardness (F = 1106.158, P < 0.001). Scanning and atomic force microscopy revealed a nanoporous surface characteristic of SIE, and FS resulted in the creation of surface microbeads, while LPPA resulted in limited abrasion of the surface. Conclusion. Within the limitations of the study, changes in surface characteristics and topography of zirconia implants have been observed after different surface treatment approaches. Thus possibilities for enhanced osseointegration could be additionally offered. PMID:25349610

Distribution of curvature of 3D nonrotational surfaces approximating the corneal topography

NASA Astrophysics Data System (ADS)

Kasprzak, Henryk T.

1998-10-01

The first part of the paper presents the analytical curves used to approximate the corneal profile. Next, some definition of 3D surfaces curvature, like main normal sections, main radii of curvature and their orientations are given. The examples of four nonrotational 3D surfaces such as: ellipsoidal, surface based on hyperbolic cosine function, sphero-cylindrical and toroidal, approximating the corneal topography are proposed. The 3D surface and the contour plots of main radii of curvature and their orientation for four nonrotational approximation of the cornea are shown. Results of calculations are discussed from the point of view of videokeratometric images.

Europa During Voyager 2 Closest Approach

NASA Image and Video Library

1996-09-26

This color image of the Jovian moon Europa was acquired by NASA Voyager 2 during its close encounter on Jul. 9, 1979. Europa, the size of our moon, is thought to have a crust of ice perhaps 100 kilometers thick which overlies the silicate crust. The complex array of streaks indicate that the crust has been fractured and filled by materials from the interior. The lack of relief, any visible mountains or craters, on its bright limb is consistent with a thick ice crust. In contrast to its icy neighbors, Ganymede and Callisto, Europa has very few impact craters. One possible candidate is the small feature near the center of this image with radiating rays and a bright circular interior. The relative absence of features and low topography suggests the crust is young and warm a few kilometers below the surface. The tidal heating process suggested for Io also may be heating Europa's interior at a lower rate. http://photojournal.jpl.nasa.gov/catalog/PIA00459

Computer-assisted design and finite element simulation of braces for the treatment of adolescent idiopathic scoliosis using a coronal plane radiograph and surface topography.

PubMed

Pea, Rany; Dansereau, Jean; Caouette, Christiane; Cobetto, Nikita; Aubin, Carl-Éric

2018-05-01

Orthopedic braces made by Computer-Aided Design and Manufacturing and numerical simulation were shown to improve spinal deformities correction in adolescent idiopathic scoliosis while using less material. Simulations with BraceSim (Rodin4D, Groupe Lagarrigue, Bordeaux, France) require a sagittal radiograph, not always available. The objective was to develop an innovative modeling method based on a single coronal radiograph and surface topography, and assess the effectiveness of braces designed with this approach. With a patient coronal radiograph and a surface topography, the developed method allowed the 3D reconstruction of the spine, rib cage and pelvis using geometric models from a database and a free form deformation technique. The resulting 3D reconstruction converted into a finite element model was used to design and simulate the correction of a brace. The developed method was tested with data from ten scoliosis cases. The simulated correction was compared to analogous simulations performed with a 3D reconstruction built using two radiographs and surface topography (validated gold standard reference). There was an average difference of 1.4°/1.7° for the thoracic/lumbar Cobb angle, and 2.6°/5.5° for the kyphosis/lordosis between the developed reconstruction method and the reference. The average difference of the simulated correction was 2.8°/2.4° for the thoracic/lumbar Cobb angles and 3.5°/5.4° the kyphosis/lordosis. This study showed the feasibility to design and simulate brace corrections based on a new modeling method with a single coronal radiograph and surface topography. This innovative method could be used to improve brace designs, at a lesser radiation dose for the patient. Copyright © 2018 Elsevier Ltd. All rights reserved.

Humeral stress remodelling locations differ in Thoroughbred racehorses training and racing on dirt compared to synthetic racetrack surfaces.

PubMed

Dimock, A N; Hoffman, K D; Puchalski, S M; Stover, S M

2013-03-01

Veterinarians have observed a putative change in the location of humeral stress remodelling in Thoroughbred racehorses with change from dirt to synthetic racetrack surfaces. To determine whether the location and severity of humeral stress remodelling differs between Thoroughbred racehorses exercising on dirt and synthetic racetrack surfaces, the potential significance of different locations of stress remodelling, and the potential usefulness of scintigraphy for prevention of complete humeral fracture. Scintigraphic images of humeri from 841 Thoroughbred racehorses at 3 racetracks during 2 years before and after conversion from dirt to synthetic surfaces were evaluated for location and severity of lesions. The effects of surface on lesion distributions were examined using Chi-square or Fisher's exact tests. Archived fractured humeri were examined to determine the location and severity of stress remodelling associated with complete fracture. Databases were queried to determine whether racehorses with scintigraphic lesions suffered humeral fracture and whether racehorses with a complete humeral fracture had had a scintigraphic examination. Horses at synthetic racetracks had a greater proportion of distal humeral lesions, whereas horses at dirt racetracks had a greater proportion of caudoproximal lesions (P<0.001). Proximal lesions were more likely to be severe than distal lesions (P<0.001). Most complete fractures were associated with caudoproximal lesions, which were more often severe than distal lesions (P = 0.002). None of the horses with a scintigraphic lesion had a complete humeral fracture. None of the horses with a complete humeral fracture underwent scintigraphic examination. Race surface affected humeral scintigraphic lesion location and hence the location of stress remodelling. Lesion severity was associated with lesion location. Complete humeral fracture was associated with caudoproximal stress remodelling and lack of scintigraphic examination. Risk for complete humeral fracture may be lower on synthetic surfaces than on dirt surfaces, and, by inference, for horses examined using scintigraphy. © 2012 EVJ Ltd.

Effective Wettability of Heterogenous Fracture Surfaces Using the Lattice-Boltzmann Method

NASA Astrophysics Data System (ADS)

E Santos, J.; Prodanovic, M.; Landry, C. J.

2017-12-01

Fracture walls in the subsurface are often structured by minerals of different composition (potentially further altered in contact with fluids during hydrocarbon extraction or CO2 sequestration), this yields in a heterogeneous wettability of the surface in contact with the fluids. The focus of our work is to study how surfaces presenting different mineralogy and roughness affect multiphase flow in fractures. Using the Shan-Chen model of the lattice-Boltzmann method (LBM) we define fluid interaction and surface attraction parameters to simulate a system of a wetting and a non-wetting fluid. In this work, we use synthetically created fractures presenting different arrangements of wetting and non-wetting patches, and with or without roughness; representative of different mineralogy, similar workflow can be applied to fractures extracted from X-ray microtomography images of fractures porous media. The results from the LBM simulations provide an insight on how the distribution of mineralogy and surface roughness are related with the observed macroscopic contact angle. We present a comparison between the published analytical models, and our results based on surface areas, spatial distribution and local fracture aperture. The understanding of the variables that affect the contact angle is useful for the comprehension of multiphase processes in naturally fractured reservoirs like primary oil production, enhanced oil recovery and CO2 sequestration. The macroscopic contact angle analytical equations for heterogeneous surfaces with variable roughness are no longer valid in highly heterogeneous systems; we quantify the difference thus offering an alternative to analytical models.

Development of Nomarski microscopy for quantitative determination of surface topography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartman, J. S.; Gordon, R. L.; Lessor, D. L.

1979-01-01

The use of Nomarski differential interference contrast (DIC) microscopy has been extended to provide nondestructive, quantitative analysis of a sample's surface topography. Theoretical modeling has determined the dependence of the image intensity on the microscope's optical components, the sample's optical properties, and the sample's surface orientation relative to the microscope. Results include expressions to allow the inversion of image intensity data to determine sample surface slopes. A commercial Nomarski system has been modified and characterized to allow the evaluation of the optical model. Data have been recorded with smooth, planar samples that verify the theoretical predictions.

Effects of a hybrid micro/nanorod topography-modified titanium implant on adhesion and osteogenic differentiation in rat bone marrow mesenchymal stem cells.

PubMed

Zhang, Wenjie; Li, Zihui; Huang, Qingfeng; Xu, Ling; Li, Jinhua; Jin, Yuqin; Wang, Guifang; Liu, Xuanyong; Jiang, Xinquan

2013-01-01

Various methods have been used to modify titanium implant surfaces with the aim of achieving better osseointegration. In this study, we fabricated a clustered nanorod structure on an acid-etched, microstructured titanium plate surface using hydrogen peroxide. We also evaluated biofunctionalization of the hybrid micro/nanorod topography on rat bone marrow mesenchymal stem cells. Scanning electron microscopy and x-ray diffraction were used to investigate the surface topography and phase composition of the modified titanium plate. Rat bone marrow mesenchymal stem cells were cultured and seeded on the plate. The adhesion ability of the cells was then assayed by cell counting at one, 4, and 24 hours after cell seeding, and expression of adhesion-related protein integrin β1 was detected by immunofluorescence. In addition, a polymerase chain reaction assay, alkaline phosphatase and Alizarin Red S staining assays, and osteopontin and osteocalcin immunofluorescence analyses were used to evaluate the osteogenic differentiation behavior of the cells. The hybrid micro/nanoscale texture formed on the titanium surface enhanced the initial adhesion activity of the rat bone marrow mesenchymal stem cells. Importantly, the hierarchical structure promoted osteogenic differentiation of these cells. This study suggests that a hybrid micro/nanorod topography on a titanium surface fabricated by treatment with hydrogen peroxide followed by acid etching might facilitate osseointegration of a titanium implant in vivo.

Effects of fracture surface roughness and shear displacement on geometrical and hydraulic properties of three-dimensional crossed rock fracture models

NASA Astrophysics Data System (ADS)

Huang, Na; Liu, Richeng; Jiang, Yujing; Li, Bo; Yu, Liyuan

2018-03-01

While shear-flow behavior through fractured media has been so far studied at single fracture scale, a numerical analysis of the shear effect on the hydraulic response of 3D crossed fracture model is presented. The analysis was based on a series of crossed fracture models, in which the effects of fracture surface roughness and shear displacement were considered. The rough fracture surfaces were generated using the modified successive random additions (SRA) algorithm. The shear displacement was applied on one fracture, and at the same time another fracture shifted along with the upper and lower surfaces of the sheared fracture. The simulation results reveal the development and variation of preferential flow paths through the model during the shear, accompanied by the change of the flow rate ratios between two flow planes at the outlet boundary. The average contact area accounts for approximately 5-27% of the fracture planes during shear, but the actual calculated flow area is about 38-55% of the fracture planes, which is much smaller than the noncontact area. The equivalent permeability will either increase or decrease as shear displacement increases from 0 to 4 mm, depending on the aperture distribution of intersection part between two fractures. When the shear displacement continuously increases by up to 20 mm, the equivalent permeability increases sharply first, and then keeps increasing with a lower gradient. The equivalent permeability of rough fractured model is about 26-80% of that calculated from the parallel plate model, and the equivalent permeability in the direction perpendicular to shear direction is approximately 1.31-3.67 times larger than that in the direction parallel to shear direction. These results can provide a fundamental understanding of fluid flow through crossed fracture model under shear.

Implications of MOLA Global Roughness, Statistics, and Topography

NASA Technical Reports Server (NTRS)

Aharonson, O.; Zuber, M. T.; Neumann, G. A.

1999-01-01

New insights are emerging as the ongoing high-quality measurements of the Martian surface topography by Mars Orbiter Laser Altimeter (MOLA) on board the Mars Global Surveyor (MGS) spacecraft increase in coverage, resolution, and diversity. For the first time, a global characterization of the statistical properties of topography is possible. The data were collected during the aerobreaking hiatus, science phasing, and mapping orbits of MGS, and have a resolution of 300-400 m along track, a range resolution of 37.5 cm, a range precision of 1-10 m for surface slopes up to 30 deg., and an absolute accuracy of topography of 13 m. The spacecraft's orbit inclination dictates that nadir observations have latitude coverage of about 87.1S to 87.1N; the addition of observations obtained during a period of off-nadir pointing over the north pole extended coverage to 90N. Additional information is contained in the original extended abstract.

The Use of Atomic-Force Microscopy for Studying the Crystallization Process of Amorphous Alloys

NASA Astrophysics Data System (ADS)

Elmanov, G. N.; Ivanitskaya, E. A.; Dzhumaev, P. S.; Skrytniy, V. I.

The crystallization process of amorphous alloys is accompanied by the volume changes as a result of structural phase transitions. This leads to changes in the surface topography, which was studied by atomic force microscopy (AFM). The changes of the surface topography, structure and phase composition during multistage crystallization process of the metallic glasses with composition Ni71,5Cr6,8Fe2,7B11,9Si7,1 and Ni63,4Cr7,4Fe4,3Mn0,8B15,6Si8,5 (AWS BNi2) has been investigated. The obtained results on changing of the surface topography in crystallization process are in good agreement with the data of X-ray diffraction analysis (XRD). The nature of redistribution of some alloy components in the crystallization process has been suggested.

Fractal characterization of fracture surfaces in concrete

USGS Publications Warehouse

Saouma, V.E.; Barton, C.C.; Gamaleldin, N.A.

1990-01-01

Fractal geometry is used to characterize the roughness of cracked concrete surfaces through a specially built profilometer, and the fractal dimension is subsequently correlated to the fracture toughness and direction of crack propagation. Preliminary results indicate that the fracture surface is indeed fractal over two orders of magnitudes with a dimension of approximately 1.20. ?? 1990.

Effect of overglazed and polished surface finishes on the compressive fracture strength of machinable ceramic materials.

PubMed

Asai, Tetsuya; Kazama, Ryunosuke; Fukushima, Masayoshi; Okiji, Takashi

2010-11-01

Controversy prevails over the effect of overglazing on the fracture strength of ceramic materials. Therefore, the effects of different surface finishes on the compressive fracture strength of machinable ceramic materials were investigated in this study. Plates prepared from four commercial brands of ceramic materials were either surface-polished or overglazed (n=10 per ceramic material for each surface finish), and bonded to flat surfaces of human dentin using a resin cement. Loads at failure were determined and statistically analyzed using two-way ANOVA and Bonferroni test. Although no statistical differences in load value were detected between polished and overglazed groups (p>0.05), the fracture load of Vita Mark II was significantly lower than those of ProCAD and IPS Empress CAD, whereas that of IPS e.max CAD was significantly higher than the latter two ceramic materials (p<0.05). It was concluded that overglazed and polished surfaces produced similar compressive fracture strengths irrespective of the machinable ceramic material tested, and that fracture strength was material-dependent.

Using well casing as an electrical source to monitor hydraulic fracture fluid injection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilt, Michael; Nieuwenhuis, Greg; MacLennan, Kris

2016-03-09

The depth to surface resistivity (DSR) method transmits current from a source located in a cased or openhole well to a distant surface return electrode while electric field measurements are made at the surface over the target of interest. This paper presents both numerical modelling results and measured data from a hydraulic fracturing field test where conductive water was injected into a resistive shale reservoir during a hydraulic fracturing operation. Modelling experiments show that anomalies due to hydraulic fracturing are small but measureable with highly sensitive sensor technology. The field measurements confirm the model results,showing that measured differences in themore » surface fields due to hydraulic fracturing have been detected above the noise floor. Our results show that the DSR method is sensitive to the injection of frac fluids; they are detectable above the noise floor in a commercially active hydraulic fracturing operation, and therefore this method can be used for monitoring fracture fluid movement.« less

The dynamical control of subduction parameters on surface topography

NASA Astrophysics Data System (ADS)

Crameri, F.; Lithgow-Bertelloni, C. R.; Tackley, P. J.

2017-04-01

The long-wavelength surface deflection of Earth's outermost rocky shell is mainly controlled by large-scale dynamic processes like isostasy or mantle flow. The largest topographic amplitudes are therefore observed at plate boundaries due to the presence of large thermal heterogeneities and strong tectonic forces. Distinct vertical surface deflections are particularly apparent at convergent plate boundaries mostly due to the convergence and asymmetric sinking of the plates. Having a mantle convection model with a free surface that is able to reproduce both realistic single-sided subduction and long-wavelength surface topography self-consistently, we are now able to better investigate this interaction. We separate the topographic signal into distinct features and quantify the individual topographic contribution of several controlling subduction parameters. Results are diagnosed by splitting the topographic signal into isostatic and residual components, and by considering various physical aspects like viscous dissipation during plate bending. Performing several systematic suites of experiments, we are then able to quantify the topographic impact of the buoyancy, rheology, and geometry of the subduction-zone system to each and every topographic feature at a subduction zone and to provide corresponding scaling laws. We identify slab dip and, slightly less importantly, slab buoyancy as the major agents controlling surface topography at subduction zones on Earth. Only the island-arc high and the back-arc depression extent are mainly controlled by plate strength. Overall, his modeling study sets the basis to better constrain deep-seated mantle structures and their physical properties via the observed surface topography on present-day Earth and back through time.

Surface topography and chemistry shape cellular behavior on wide band-gap semiconductors.

PubMed

Bain, Lauren E; Collazo, Ramon; Hsu, Shu-Han; Latham, Nicole Pfiester; Manfra, Michael J; Ivanisevic, Albena

2014-06-01

The chemical stability and electrical properties of gallium nitride make it a promising material for the development of biocompatible electronics, a range of devices including biosensors as well as interfaces for probing and controlling cellular growth and signaling. To improve the interface formed between the probe material and the cell or biosystem, surface topography and chemistry can be applied to modify the ways in which the device interacts with its environment. PC12 cells are cultured on as-grown planar, unidirectionally polished, etched nanoporous and nanowire GaN surfaces with and without a physisorbed peptide sequence that promotes cell adhesion. While cells demonstrate preferential adhesion to roughened surfaces over as-grown flat surfaces, the topography of that roughness also influences the morphology of cellular adhesion and differentiation in neurotypic cells. Addition of the peptide sequence generally contributes further to cellular adhesion and promotes development of stereotypic long, thin neurite outgrowths over alternate morphologies. The dependence of cell behavior on both the topographic morphology and surface chemistry is thus demonstrated, providing further evidence for the importance of surface modification for modulating bio-inorganic interfaces. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Cold Gas-Sprayed Deposition of Metallic Coatings onto Ceramic Substrates Using Laser Surface Texturing Pre-treatment

NASA Astrophysics Data System (ADS)

Kromer, R.; Danlos, Y.; Costil, S.

2018-04-01

Cold spraying enables a variety of metals dense coatings onto metal surfaces. Supersonic gas jet accelerates particles which undergo with the substrate plastic deformation. Different bonding mechanisms can be created depending on the materials. The particle-substrate contact time, contact temperature and contact area upon impact are the parameters influencing physicochemical and mechanical bonds. The resultant bonding arose from plastic deformation of the particle and substrate and temperature increasing at the interface. The objective was to create specific topography to enable metallic particle adhesion onto ceramic substrates. Ceramic did not demonstrate deformation during the impact which minimized the intimate bonds. Laser surface texturing was hence used as prior surface treatment to create specific topography and to enable mechanical anchoring. Particle compressive states were necessary to build up coating. The coating deposition efficiency and adhesion strength were evaluated. Textured surface is required to obtain strong adhesion of metallic coatings onto ceramic substrates. Consequently, cold spray coating parameters depend on the target material and a methodology was established with particle parameters (diameters, velocities, temperatures) and particle/substrate properties to adapt the surface topography. Laser surface texturing is a promising tool to increase the cold spraying applications.

Shape-from-shading using Landsat 8 and airborne laser altimetry over ice sheets: toward new regional DEMs of Greenland and Antarctica

NASA Astrophysics Data System (ADS)

Moussavi, M. S.; Scambos, T.; Haran, T. M.; Klinger, M. J.; Abdalati, W.

2015-12-01

We investigate the capability of Landsat 8's Operational Land Imager (OLI) instrument to quantify subtle ice sheet topography of Greenland and Antarctica. We use photoclinometry, or 'shape-from-shading', a method of deriving surface topography from local variations in image brightness due to varying surface slope. Photoclinomeetry is applicable over ice sheet areas with highly uniform albedo such as regions covered by recent snowfall. OLI imagery is available from both ascending and descending passes near the summer solstice period for both ice sheets. This provides two views of the surface features from two distinct solar azimuth illumination directions. Airborne laser altimetry data from the Airborne Topographic Mapper (ATM) instrument (flying on the Operation Ice Bridge program) are used to quantitatively convert the image brightness variations of surface undulations to surface slope. To validate the new DEM products, we use additional laser altimetry profiles collected over independent sites from Ice Bridge and ICESat, and high-resolution WorldView-2 DEMs. The photoclinometry-derived DEM products will be useful for studying surface elevation changes, enhancing bedrock elevation maps through inversion of surface topography, and inferring local variations in snow accumulation rates.

Fracture surface analysis of a quenched (α+β)-metastable titanium alloy

NASA Astrophysics Data System (ADS)

Illarionov, A. G.; Stepanov, S. I.; Demakov, S. L.

2017-12-01

Fracture surface analysis is conducted by means of SEM for VT16 titanium alloy specimens solution-treated at temperatures ranging from 700 to 875 °C, water-quenched and subjected to tensile testing. A cup and cone shape failure and dimple microstructure of the fracture surface indicates the ductile behavior of the alloy. Dimple dimensions correlated with the β-grain size of the alloy in quenched condition. The fracture area (namely, the size; the cup and cone shape) depends on the volume fraction of the primary α-phase in the quenched sample. However, the fracture surface changes considerably when the strain-induced β-αʺ-transformation takes place during tensile testing, resulting in the increase of alloy ductility.

Viscous relaxation as a prerequisite for tectonic resurfacing on Ganymede: Insights from numerical models of lithospheric extension

USGS Publications Warehouse

Bland, Michael T.; McKinnon, William B.

2018-01-01

Ganymede’s bright terrain formed during a near-global resurfacing event (or events) that produced both heavily tectonized and relatively smooth terrains. The mechanism(s) by which resurfacing occurred on Ganymede (e.g., cryovolcanic or tectonic), and the relationship between the older, dark and the younger, bright terrain are fundamental to understanding the geological evolution of the satellite. Using a two-dimensional numerical model of lithospheric extension that has previously been used to successfully simulate surface deformation consistent with grooved terrain morphologies, we investigate whether large-amplitude preexisting topography can be resurfaced (erased) by extension (i.e., tectonic resurfacing). Using synthetically produced initial topography, we show that when the total relief of the initial topography is larger than 25–50 m, periodic groove-like structures fail to form. Instead, extension is localized in a few individual, isolated troughs. These results pose a challenge to the tectonic resurfacing hypothesis. We further investigate the effects of preexisting topography by performing suites of simulations initialized with topography derived from digital terrain models of Ganymede’s surface. These include dark terrain, fresh (relatively deep) impact craters, smooth bright terrain, and a viscously relaxed impact crater. The simulations using dark terrain and fresh impact craters are consistent with our simulations using synthetic topography: periodic groove-like deformation fails to form. In contrast, when simulations were initialized with bright smooth terrain topography, groove-like deformation results from a wide variety of heat flow and surface temperature conditions. Similarly, when a viscously relaxed impact crater was used, groove-like structures were able to form during extension. These results suggest that tectonic resurfacing may require that the amplitude of the initial topography be reduced before extension begins. We emphasize that viscous relaxation may be the key to enabling tectonic resurfacing, as the heat fluxes associated with groove terrain formation are also capable of reducing crater topography through viscous relaxation. For long-wavelength topography (large craters) viscous relaxation is unavoidable. We propose that the resurfacing of Ganymede occurred through a combination of viscous relaxation, tectonic resurfacing, cryovolcanism and, at least in a few cases, band formation. Variations in heat flow and strain magnitudes across Ganymede likely produced the complex variety of terrain types currently observed.

Viscous relaxation as a prerequisite for tectonic resurfacing on Ganymede: Insights from numerical models of lithospheric extension

NASA Astrophysics Data System (ADS)

Bland, Michael T.; McKinnon, William B.

2018-05-01

Ganymede's bright terrain formed during a near-global resurfacing event (or events) that produced both heavily tectonized and relatively smooth terrains. The mechanism(s) by which resurfacing occurred on Ganymede (e.g., cryovolcanic or tectonic), and the relationship between the older, dark and the younger, bright terrain are fundamental to understanding the geological evolution of the satellite. Using a two-dimensional numerical model of lithospheric extension that has previously been used to successfully simulate surface deformation consistent with grooved terrain morphologies, we investigate whether large-amplitude preexisting topography can be resurfaced (erased) by extension (i.e., tectonic resurfacing). Using synthetically produced initial topography, we show that when the total relief of the initial topography is larger than 25-50 m, periodic groove-like structures fail to form. Instead, extension is localized in a few individual, isolated troughs. These results pose a challenge to the tectonic resurfacing hypothesis. We further investigate the effects of preexisting topography by performing suites of simulations initialized with topography derived from digital terrain models of Ganymede's surface. These include dark terrain, fresh (relatively deep) impact craters, smooth bright terrain, and a viscously relaxed impact crater. The simulations using dark terrain and fresh impact craters are consistent with our simulations using synthetic topography: periodic groove-like deformation fails to form. In contrast, when simulations were initialized with bright smooth terrain topography, groove-like deformation results from a wide variety of heat flow and surface temperature conditions. Similarly, when a viscously relaxed impact crater was used, groove-like structures were able to form during extension. These results suggest that tectonic resurfacing may require that the amplitude of the initial topography be reduced before extension begins. We emphasize that viscous relaxation may be the key to enabling tectonic resurfacing, as the heat fluxes associated with groove terrain formation are also capable of reducing crater topography through viscous relaxation. For long-wavelength topography (large craters) viscous relaxation is unavoidable. We propose that the resurfacing of Ganymede occurred through a combination of viscous relaxation, tectonic resurfacing, cryovolcanism and, at least in a few cases, band formation. Variations in heat flow and strain magnitudes across Ganymede likely produced the complex variety of terrain types currently observed.

Critical zone architecture and processes: a geophysical perspective

NASA Astrophysics Data System (ADS)

Holbrook, W. S.

2016-12-01

The "critical zone (CZ)," Earth's near-surface layer that reaches from treetop to bedrock, sustains terrestrial life by storing water and producing nutrients. Despite is central importance, however, the CZ remains poorly understood, due in part to the complexity of interacting biogeochemical and physical processes that take place there, and in part due to the difficulty of measuring CZ properties and processes at depth. Major outstanding questions include: What is the architecture of the CZ? How does that architecture vary across scales and across gradients in climate, lithology, topography, biology and regional states of stress? What processes control the architecture of the CZ? At what depth does weathering initiate, and what controls the rates at which it proceeds? Based on recent geophysical campaigns at seven Critical Zone Observatory (CZO) sites and several other locations, a geophysical perspective on CZ architecture and processes is emerging. CZ architecture can be usefully divided into four layers, each of which has distinct geophysical properties: soil, saprolite, weathered bedrock and protolith. The distribution of those layers across landscapes varies depending on protolith composition and internal structure, topography, climate (P/T) and the regional state of stress. Combined observations from deep CZ drilling, geophysics and geochemistry demonstrate that chemical weathering initiates deep in the CZ, in concert with mechanical weathering (fracturing), as chemical weathering appears concentrated along fractures in borehole walls. At the Calhoun CZO, the plagioclase weathering front occurs at nearly 40 m depth, at the base of a 25-m-thick layer of weathered bedrock. The principal boundary in porosity, however, occurs at the saprolite/weathered bedrock boundary: porosity decreases over an order of magnitude, from 50% to 5% over an 8-m-thick zone at the base of saprolite. Porosity in weathered bedrock is between 2-5%. Future progress will depend on (1) more tightly linked geophysical, geochemical, hydrological and drilling studies, (2) 3D and 4D studies of deep CZ structure, and (3) measurements at multiple scales in the CZ, from pores to plots to hillslopes to catchments.

The Influence of Topography on Subaqueous Sediment Gravity Flows and the Resultant Deposits: Examples from Deep-water Systems in Offshore Morocco and Offshore Trinidad

NASA Astrophysics Data System (ADS)

Deng, H.; Wood, L.; Overeem, I.; Hutton, E.

2016-12-01

Submarine topography has a fundamental control on the movement of sediment gravity flows as well as the distribution, morphology, and internal heterogeneity of resultant overlying, healing-phase, deep-water reservoirs. Some of the most complex deep-water topography is generated through both destructive and constructive mass transport processes. A series of numerical models using Sedflux software have been constructed over high resolution mass transport complexes (MTCs) top paleobathymetric surfaces mapped from 3D seismic data in offshore Morocco and offshore eastern Trinidad. Morocco's margin is characterized by large, extant rafted blocks and a flow perpendicular fabric. Trinidad's margin is characterized by muddier, plastic flows and isolated extrusive diapiric buttresses. In addition, Morocco's margin is a dry, northern latitude margin that lacks major river inputs, while Trinidad's margin is an equatorial, wet climate that is fed by the Orinoco River and delta. These models quantitatively delineate the interaction of healing-phase gravity flows on the tops of two very different topographies and provide insights into healing-phase reservoir distribution and stratigraphic trap development. Slopes roughness, curvatures, and surface shapes are measured and quantified relative to input points to quantify depositional surface character. A variety of sediment gravity flow types have been input and the resultant interval assessed for thickness and distribution relative to key topography parameters. Mathematical relationships are to be analyzed and compared with seismic data interpretation of healing-phase interval character, toward an improved model of gravity sedimentation and topography interactions.

Dynamic Mechanical Properties and Fracture Surface Morphologies of Core-Shell Rubber (CSR) Toughened Epoxy at Liquid Nitrogen (Ln2) Temperatures

NASA Technical Reports Server (NTRS)

Wang, J.; Magee, D.; Schneider, J. A.

2009-01-01

The dynamic mechanical properties and fracture surface morphologies were evaluated for a commercial epoxy resin toughened with two types of core-shell rubber (CSR) toughening agents (Kane Ace(Registered TradeMark) MX130 and MX960). The impact resistance (R) was evaluated by the resulting breaking energy measured in Charpy impact tests conducted on an instrumented drop tower. The resulting fracture surface morphologies were examined using Scanning Electron Microscopy (SEM). Fractographic observations of the CSR toughened epoxy tested at ambient temperature, showed a fracture as characterized by slender dendrite textures with large voids. The increasing number of dendrites and decreasing size of scale-like texture with more CSR particles corresponded with increased R. As the temperature decreased to Liquid Nitrogen (LN 2), the fracture surfaces showed a fracture characterized by a rough, torn texture containing many river markings and deep furrows.

EAARL topography-Potato Creek watershed, Georgia, 2010

USGS Publications Warehouse

Bonisteel-Cormier, J.M.; Nayegandhi, Amar; Fredericks, Xan; Jones, J.W.; Wright, C.W.; Brock, J.C.; Nagle, D.B.

2011-01-01

This DVD contains lidar-derived first-surface (FS) and bare-earth (BE) topography GIS datasets of a portion of the Potato Creek watershed in the Apalachicola-Chattahoochee-Flint River basin, Georgia. These datasets were acquired on February 27, 2010.

Apparent Brightness and Topography Images of Vibidia Crater

NASA Image and Video Library

2012-03-09

The left-hand image from NASA Dawn spacecraft shows the apparent brightness of asteroid Vesta surface. The right-hand image is based on this apparent brightness image, with a color-coded height representation of the topography overlain onto it.

Topography of Troughs on Vesta

NASA Image and Video Library

2011-08-23

This view of the topography of asteroid Vesta surface is composed of several images obtained with the clear filter in the framing camera on NASA Dawn spacecraft on August 6, 2011. The image has a resolution of about 260 meters per pixel.

a Predictive Model of Permeability for Fractal-Based Rough Rock Fractures during Shear

NASA Astrophysics Data System (ADS)

Huang, Na; Jiang, Yujing; Liu, Richeng; Li, Bo; Zhang, Zhenyu

This study investigates the roles of fracture roughness, normal stress and shear displacement on the fluid flow characteristics through three-dimensional (3D) self-affine fractal rock fractures, whose surfaces are generated using the modified successive random additions (SRA) algorithm. A series of numerical shear-flow tests under different normal stresses were conducted on rough rock fractures to calculate the evolutions of fracture aperture and permeability. The results show that the rough surfaces of fractal-based fractures can be described using the scaling parameter Hurst exponent (H), in which H = 3 - Df, where Df is the fractal dimension of 3D single fractures. The joint roughness coefficient (JRC) distribution of fracture profiles follows a Gauss function with a negative linear relationship between H and average JRC. The frequency curves of aperture distributions change from sharp to flat with increasing shear displacement, indicating a more anisotropic and heterogeneous flow pattern. Both the mean aperture and permeability of fracture increase with the increment of surface roughness and decrement of normal stress. At the beginning of shear, the permeability increases remarkably and then gradually becomes steady. A predictive model of permeability using the mean mechanical aperture is proposed and the validity is verified by comparisons with the experimental results reported in literature. The proposed model provides a simple method to approximate permeability of fractal-based rough rock fractures during shear using fracture aperture distribution that can be easily obtained from digitized fracture surface information.

From brittle to ductile fracture in disordered materials.

PubMed

Picallo, Clara B; López, Juan M; Zapperi, Stefano; Alava, Mikko J

2010-10-08

We introduce a lattice model able to describe damage and yielding in heterogeneous materials ranging from brittle to ductile ones. Ductile fracture surfaces, obtained when the system breaks once the strain is completely localized, are shown to correspond to minimum energy surfaces. The similarity of the resulting fracture paths to the limits of brittle fracture or minimum energy surfaces is quantified. The model exhibits a smooth transition from brittleness to ductility. The dynamics of yielding exhibits avalanches with a power-law distribution.

Effect of polymer properties and adherend surfaces on adhesion

NASA Technical Reports Server (NTRS)

Dwight, D. W.; Wightman, J. P.

1976-01-01

High temperature polymer surface characteristics associated with joint strength were evaluated. Selected samples represented composite adherends, aluminum filler and fiber glass carrier cloth. Detailed analysis of fractured joint surfaces revealed unique characteristics typical of the specific adhesive formulations and test conditions. A fracture mechanism model was developed for correlating macroscopic shear strength and microstructure of fracture surfaces. Applications were made to unpublished data on polyimides and fluoropolymers.

Assessing the Impact of Topography on Groundwater Salinization Due to Storm Surge Inundation

NASA Astrophysics Data System (ADS)

Yu, X.; Yang, J.; Graf, T.; Koneshloo, M.; O'Neal, M. A.; Michael, H. A.

2015-12-01

The sea-level rise and increase in the frequency and intensity of coastal storms due to climate change are likely to exacerbate adverse effects of storm surges on low-lying coastal areas. The landward flow of water during storm surges introduces salt to surficial coastal aquifers and threatens groundwater resources. Coastal topography (e.g. ponds, dunes, canals) likely has a strong impact on overwash and salinization processes, but is generally highly simplified in modeling studies. To understand the topographic impacts on groundwater salinization, we modeled overwash and variable-density groundwater flow and salt transport in 3D using the fully coupled surface and subsurface numerical simulator, HydroGeoSphere. The model simulates the coastal aquifer as an integrated system considering processes such as overland flow, coupled surface and subsurface exchange, variably saturated flow, and variable-density flow. To represent various coastal landscape types, we started with realistic coastal topography from Delaware, USA, and then generated synthetic fields with differing shore-perpendicular connectivity and surface depressions. The groundwater salinization analysis suggested that the topographic connectivity promoting overland flow controls the volume of aquifer that is salinized. In contrast, depression storage of surface water mainly controls the time for infiltrated salt to flush from the aquifer. The results indicate that for a range of synthetic conditions, topography increases the flushing time of salt by 20-300% relative to an equivalent "simple slope" in which topographic variation is absent. Our study suggests that topography have a significant impact on overwash salinization, with important implications for land management at local scales and groundwater vulnerability assessment at regional to global scales.

Bathymetric Atlas of the North Pacific Ocean.

DTIC Science & Technology

1978-01-01

U.S. Coast and Geodetic Survey provided nearshore from Novel Oceenoglphic Office neutical chert of various detils around islands and reefs. Nautical...Easter Islands , 1961. Middle America Trench: Topography and struc- Bernice P. Bishop Mus. Bull. 110, p. 1-44. ture, Geol. Sec. Amer. Bull., v. 72, p...of volcanic ash layers and turbidito% ini 1956. Clipperton fracture zone in the northeastern equa- the north Pacific, Gal. Soc. Amer. Bull., v. 80, p

Pattern, age, and origin of structural features within the Ozark plateau and the relationship to ore deposits

NASA Technical Reports Server (NTRS)

Arvidson, R. E.

1981-01-01

Topography and gravity anomaly images for the continental United States were constructed. Evidence was found based on gravity, remote sensing data, the presence, trend, and character of fractures, and on rock type data, for a Precambrian rift through Missouri. The feature is probably the failed arm of a triple junction that existed prior to formation of the granite-rhyolite terrain of southern Missouri.

Surface polishing of niobium for superconducting radio frequency (SRF) cavity applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Liang

2014-08-01

Niobium cavities are important components in modern particle accelerators based on superconducting radio frequency (SRF) technology. The interior of SRF cavities are cleaned and polished in order to produce high accelerating field and low power dissipation on the cavity wall. Current polishing methods, buffered chemical polishing (BCP) and electro-polishing (EP), have their advantages and limitations. We seek to improve current methods and explore laser polishing (LP) as a greener alternative of chemical methods. The topography and removal rate of BCP at different conditions (duration, temperature, sample orientation, flow rate) was studied with optical microscopy, scanning electron microscopy (SEM), and electronmore » backscatter diffraction (EBSD). Differential etching on different crystal orientations is the main contributor to fine grain niobium BCP topography, with gas evolution playing a secondary role. The surface of single crystal and bi-crystal niobium is smooth even after heavy BCP. The topography of fine grain niobium depends on total removal. The removal rate increases with temperature and surface acid flow rate within the rage of 0~20 °C, with chemical reaction being the possible dominate rate control mechanism. Surface flow helps to regulate temperature and avoid gas accumulation on the surface. The effect of surface flow rate on niobium EP was studied with optical microscopy, atomic force microscopy (AFM), and power spectral density (PSD) analysis. Within the range of 0~3.7 cm/s, no significant difference was found on the removal rate and the macro roughness. Possible improvement on the micro roughness with increased surface flow rate was observed. The effect of fluence and pulse accumulation on niobium topography during LP was studied with optical microscopy, SEM, AFM, and PSD analysis. Polishing on micro scale was achieved within fluence range of 0.57~0.90 J/cm2, with pulse accumulation adjusted accordingly. Larger area treatment was proved possible by overlapping laser tracks at proper ratio. Comparison of topography and PSD indicates that LP smooths the surface in a way similar to EP. The optimized LP parameters were applied to different types of niobium surfaces representing different stages in cavity fabrication. LP reduces the sharpness on rough surfaces effectively, while doing no harm to smooth surfaces. Secondary ion mass spectrometer (SIMS) analysis showed that LP reduces the oxide layer slightly and no contamination occurred from LP. EBSD showed no significant change on crystal structure after LP.« less

Fabrication of planarised conductively patterned diamond for bio-applications.

PubMed

Tong, Wei; Fox, Kate; Ganesan, Kumaravelu; Turnley, Ann M; Shimoni, Olga; Tran, Phong A; Lohrmann, Alexander; McFarlane, Thomas; Ahnood, Arman; Garrett, David J; Meffin, Hamish; O'Brien-Simpson, Neil M; Reynolds, Eric C; Prawer, Steven

2014-10-01

The development of smooth, featureless surfaces for biomedical microelectronics is a challenging feat. Other than the traditional electronic materials like silicon, few microelectronic circuits can be produced with conductive features without compromising the surface topography and/or biocompatibility. Diamond is fast becoming a highly sought after biomaterial for electrical stimulation, however, its inherent surface roughness introduced by the growth process limits its applications in electronic circuitry. In this study, we introduce a fabrication method for developing conductive features in an insulating diamond substrate whilst maintaining a planar topography. Using a combination of microwave plasma enhanced chemical vapour deposition, inductively coupled plasma reactive ion etching, secondary diamond growth and silicon wet-etching, we have produced a patterned substrate in which the surface roughness at the interface between the conducting and insulating diamond is approximately 3 nm. We also show that the patterned smooth topography is capable of neuronal cell adhesion and growth whilst restricting bacterial adhesion. Copyright © 2014 Elsevier B.V. All rights reserved.

Surface topography of 1€ coin measured by stereo-PIXE

NASA Astrophysics Data System (ADS)

Gholami-Hatam, E.; Lamehi-Rachti, M.; Vavpetič, P.; Grlj, N.; Pelicon, P.

2013-07-01

We demonstrate the stereo-PIXE method by measurement of surface topography of the relief details on 1€ coin. Two X-ray elemental maps were simultaneously recorded by two X-ray detectors positioned at the left and the right side of the proton microbeam. The asymmetry of the yields in the pixels of the two X-ray maps occurs due to different photon attenuation on the exit travel path of the characteristic X-rays from the point of emission through the sample into the X-ray detectors. In order to calibrate the inclination angle with respect to the X-ray asymmetry, a flat inclined surface model was at first applied for the sample in which the matrix composition and the depth elemental concentration profile is known. After that, the yield asymmetry in each image pixel was transferred into corresponding local inclination angle using calculated dependence of the asymmetry on the surface inclination. Finally, the quantitative topography profile was revealed by integrating the local inclination angle over the lateral displacement of the probing beam.

Surface topography and ordering-variant segregation in GaInP[sub 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedman, D.J.; Zhu, J.G.; Kibbler, A.E.

1993-09-27

Using transmission electron diffraction dark-field imaging, atomic force microscopy (AFM), and Nomarski microscopy, we demonstrate a direct connection between surface topography and cation site ordering in GaInP[sub 2]. We study epilayers grown by organometallic vapor-phase epitaxy on GaAs substrates oriented 2[degree] off (100) towards (110). Nomarski microscopy shows that, as growth proceeds, the surface of ordered material forms faceted structures aligned roughly along [011]. A comparison with the dark-field demonstrates that the [1[bar 1]1] and [11[bar 1

Dual interferometer for dynamic measurement of corneal topography

NASA Astrophysics Data System (ADS)

Micali, Jason D.; Greivenkamp, John E.

2016-08-01

The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface, where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. A dual interferometer system for measuring the dynamic corneal topography is designed, built, verified, and qualified by testing on human subjects. The system consists of two coaligned simultaneous phase-shifting polarization-splitting Twyman-Green interferometers. The primary interferometer measures the surface of the tear film while the secondary interferometer tracks the absolute position of the cornea, which provides enough information to reconstruct the absolute shape of the cornea. The results are high-resolution and high-accuracy surface topography measurements of the in vivo tear film and cornea that are captured at standard camera frame rates.

Outcrop-scale fracture trace identification using surface roughness derived from a high-density point cloud

NASA Astrophysics Data System (ADS)

Okyay, U.; Glennie, C. L.; Khan, S.

2017-12-01

Owing to the advent of terrestrial laser scanners (TLS), high-density point cloud data has become increasingly available to the geoscience research community. Research groups have started producing their own point clouds for various applications, gradually shifting their emphasis from obtaining the data towards extracting more and meaningful information from the point clouds. Extracting fracture properties from three-dimensional data in a (semi-)automated manner has been an active area of research in geosciences. Several studies have developed various processing algorithms for extracting only planar surfaces. In comparison, (semi-)automated identification of fracture traces at the outcrop scale, which could be used for mapping fracture distribution have not been investigated frequently. Understanding the spatial distribution and configuration of natural fractures is of particular importance, as they directly influence fluid-flow through the host rock. Surface roughness, typically defined as the deviation of a natural surface from a reference datum, has become an important metric in geoscience research, especially with the increasing density and accuracy of point clouds. In the study presented herein, a surface roughness model was employed to identify fracture traces and their distribution on an ophiolite outcrop in Oman. Surface roughness calculations were performed using orthogonal distance regression over various grid intervals. The results demonstrated that surface roughness could identify outcrop-scale fracture traces from which fracture distribution and density maps can be generated. However, considering outcrop conditions and properties and the purpose of the application, the definition of an adequate grid interval for surface roughness model and selection of threshold values for distribution maps are not straightforward and require user intervention and interpretation.

Rockfall susceptibility mapping of Yosemite Valley (USA) using a high-resolution digital elevation model

NASA Astrophysics Data System (ADS)

Pannatier, A.; Oppikofer, T.; Jaboyedoff, M.; Stock, G. M.

2009-04-01

In Yosemite National Park (California, USA) rockfalls from the steep valley flanks are frequent (>600 documented events in 150 years) and threaten infrastructure in this popular tourist area. This study focuses on a methodology to map the susceptibility to rockfall initiation based on a high-resolution digital elevation model (HRDEM) obtained from aerial laser scanning (1 meter cell size). This methodology is based on geometric factors derived from the HRDEM, i.e., the steepness of the topography, the presence of joints or fractures enabling either a planar or a wedge failure mechanism, and a high denudation potential. The slope angle histogram computed using standard GIS routines was simulated using Gaussian distributions, which were attributed to different parts of the topography, i.e., the cliffs, the valley flanks and the valley floor. Slopes steeper than 36° are found to form cliffs and thus potentially lead to rockfalls. A morpho-structural analysis of the HRDEM was performed in Coltop3D software to determine the major discontinuity sets that shape the topography. Kinematic analyses were made for each of these 7 discontinuity sets in order to determine the HRDEM cells that fulfil the geometric criteria for a planar or wedge failure mechanism. Most of the cliffs in Yosemite Valley enable one or both of these failure mechanisms. The denudation potential was assessed using the sloping local base level (SLBL) concept. The SLBL defines a basal erosion surface and the above lying rock masses (up to 400 m in some of the vertical cliffs) are susceptible to erosion by mass wasting. A thickness of 20 m above the SLBL surface was chosen as lower limit for the denudation potential criterion. The HRDEM cells that satisfy 1, 2 or all 3 criteria are considered having low, moderate and high susceptibility to rockfall initiation. The areas with highest susceptibility (El Capitan, Glacier Point, Yosemite Falls and Half Dome) coincide well with post-glacial talus accumulations and historic rockfall sources. Compared to previous maps of potential rockfall sources that were mainly based on the slope angle criterion, this study provides a more refined analysis of potential rockfall sources and is useful for focussing detailed field investigations on those areas with high susceptibility.

A new look on anomalous thermal gradient values obtained in South Portugal

NASA Astrophysics Data System (ADS)

Duque, M. R.; Malico, I.

2012-04-01

A NEW LOOK ON THE ANOMALOUS THERMAL GRADIENT VALUES OBTAINED IN SOUTH PORTUGAL Duque, M. R. and Malico, I. M. Physics Department, University of Évora, Rua Romão Ramalho, 59,7000-671, Évora, Portugal It is well known that soil temperatures can be altered by water circulation. In this paper, we study numerically this effect by simulating some aquifers occurring in South Portugal. At this location, the thermal gradient values obtained in boreholes with depths less than 200 m, range between 22 and 30 °C km-1. However, there, it is easy to find places where temperatures are around 30 °C, at depths of 100 m. The obtained thermal gradient values show an increase one day after raining and a decrease during the dry season. Additionally, the curve of temperature as function of depth showed no hot water inlet in the hole. The region studied shows a smooth topography due to intensive erosion, but it was affected by alpine and hercinian orogenies. As a result, a high topography in depth, with folds and wrinkles is present. The space between adjacent folds is now filled by small sedimentary basins. Aquifers existing in this region can reach considerable depths and return to depths near the surface, but hot springs in the area are scarce. Water temperature rises in depth, and when the speed is high enough high temperatures near the surface, due to water circulation, can be found. The ability of the fluid to flow through the system depends on topography relief, rock permeability and basal heat flow. In this study, the steady-state fluid flow and heat transfer by conduction and advection are modeled. Fractures in the medium are simulated by an equivalent porous medium saturated with liquid. Thermal conductivity values for the water and the rocks can vary in space .Porosities used have high values in the region of the aquifer, low values in the lower region of the model and intermediate values in the upper regions. The results obtained show that temperature anomaly values depend on water ascending velocity, permeability values and depth of the aquifer. Comparing the results of our model with the measured values we can obtain information about aquifer depth and temperature.

The Compensation State of Intermediate Size Lunar Craters

NASA Astrophysics Data System (ADS)

Reindler, Lucas; Arkani-Hamed, Jafar

2001-09-01

The compensation state of 49 intermediate size (120 to 600 km diameter) lunar craters are investigated using the most recent spherical harmonic models of the lunar topography and gravity, truncated at degree n=110. The total mass anomalies per unit area (i.e., the lateral variations of the vertically integrated density perturbations per unit area) within an otherwise uniform crust of 60 km thickness are determined such that, together with the surface topography, give rise to the model gravity anomalies. Crustal thicknesses of 40 and 80 km are also considered, but the general results of this study are not significantly affected. Excess mass anomalies are obtained by subtracting from the total mass anomalies the mass anomalies that are required for the isostatic compensation of the surface topography. The excess mass anomaly of a crater denotes its particular state of compensation. Dependencies of the excess mass anomalies on crater location, size, and age are investigated, but in general few discernable trends are evident. Although the vast majority of craters indicate some compensation, no correlation exists between age or size and the state of compensation. Roughly 16% of the craters show no compensation, and in some cases have mass deficiencies most likely due to the shock fractured bedrock: the breccia lens of lower density. The crust in these regions was likely cold and rigid enough at the time of impact to rigidly support the stress caused by crater excavation. These features are seen throughout different geological periods, demonstrating that the lunar crust cooled quickly and strengthened soon after formation. A comparison of the compensation state of craters Apollo, Korolev, and Hertzsprung suggests that the thermal and mechanical properties of the crust prior to impact had an appreciable effect on the compensation, and that crustal thickness may be the single most important factor controlling the compensation of intermediate size craters. The characteristics of the excess mass a nomaly profiles of the eight well-known near side mascon basins are used to identify new mascon-like craters. Ten newly found mascons are confirmed: Humboldtianum, Moscoviense, Mendel-Rydberg, Lorentz, Hertzsprung, Korolev, Schrodinger, Freundlich-Sharonov, Coulomb-Sarton, and Schiller-Zucchius, while two more, Deslandres and Dirichlet-Jackson, are very plausible. These results show that mare flow is not necessarily required to produce mascon-like characteristics.

Cellular Responses Evoked by Different Surface Characteristics of Intraosseous Titanium Implants

PubMed Central

Feller, Liviu; Jadwat, Yusuf; Khammissa, Razia A. G.; Meyerov, Robin; Lemmer, Johan

2015-01-01

The properties of biomaterials, including their surface microstructural topography and their surface chemistry or surface energy/wettability, affect cellular responses such as cell adhesion, proliferation, and migration. The nanotopography of moderately rough implant surfaces enhances the production of biological mediators in the peri-implant microenvironment with consequent recruitment of differentiating osteogenic cells to the implant surface and stimulates osteogenic maturation. Implant surfaces with moderately rough topography and with high surface energy promote osteogenesis, increase the ratio of bone-to-implant contact, and increase the bonding strength of the bone to the implant at the interface. Certain features of implant surface chemistry are also important in enhancing peri-implant bone wound healing. It is the purpose of this paper to review some of the more important features of titanium implant surfaces which have an impact on osseointegration. PMID:25767803

Veneer Ceramic to Y-TZP Bonding: Comparison of Different Surface Treatments.

PubMed

Kirmali, Omer; Kapdan, Alper; Kustarci, Alper; Er, Kursat

2016-06-01

The purpose of this study was to evaluate the effects of various surface-treatment techniques for enhancing the bond strength between veneering ceramic and yttria-stabilized tetragonal zirconia polycrystals (Y-TZP). Pre-sintered Y-TZP specimens were divided into eight groups (n = 10) according to the surface-treatment technique used: (a) untreated (control); (b) air abrasion with aluminum oxide particles; (c) erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation at different energy intensities (1 to 6 W). All specimens were then sintered and veneered with veneering ceramic according to the manufacturer's instructions. The obtained zirconia-ceramic specimens were immersed in 37°C distilled water for 24 hours before a shear bond strength test using a universal testing device at a 1 mm/min crosshead speed. The average values were calculated. After debonding, the Y-TZP surfaces were examined under a stereomicroscope to determine their fracture pattern, and the surface topography was evaluated with scanning electron microscopy after surface treatments. The bond strength ranged from 13.24 to 20.54 MPa. All surface treatments increased the bond strength between the veneering ceramic and Y-TZP; however, the value for the 6 W irradiation group was significantly different from the values for other groups (p ˂ 0.05). The present study's findings showed that higher energy densities were needed for the laser irradiation to improve the bond strength between the veneering ceramic and zirconia. Y-TZP is commonly used as a core material in fixed restorations. The bond strength between zirconia and the veneering ceramic can be affected by various surface treatments. © 2015 by the American College of Prosthodontists.

EAARL coastal topography-Assategue Island National Seashore, Maryland and Virginia, 2010

USGS Publications Warehouse

Bonisteel-Cormier, J.M.; Nayegandhi, Amar; Wright, C.W.; Brock, J.C.; Nagle, D.B.; Vivekanandan, Saisudha; Klipp, E.S.; Fredericks, Xan; Stevens, Sara

2011-01-01

This DVD contains lidar-derived bare-earth (BE) and first-surface (FS) topography GIS datasets of a portion of the Assateague Island National Seashore in Maryland and Virginia. These datasets were acquired on March 19 and 24, 2010.

EAARL topography-Three Mile Creek and Mobile-Tensaw Delta, Alabama, 2010

USGS Publications Warehouse

Nayegandhi, Amar; Bonisteel-Cormier, J.M.; Clark, A.P.; Wright, C.W.; Brock, J.C.; Nagle, D.B.; Vivekanandan, Saisudha; Fredericks, Xan

2011-01-01

This DVD contains lidar-derived first-surface (FS) and bare-earth (BE) topography GIS datasets of a portion of the Mobile-Tensaw Delta region and Three Mile Creek in Alabama. These datasets were acquired on March 6, 2010.

Topography and Roughness Signatures of Erosion of Crusted Soils on Mars

NASA Astrophysics Data System (ADS)

Cooper, C. D.; Mustard, J. F.

1999-03-01

MOLA slope and roughness data shed light on the erosion of regional duricrust and suggest it follows preexisting topography. This implies that cementation of the duricrust was likely due to atmosphere-surface interactions or in situ alteration.

Quantitative surface topography determination by Nomarski reflection microscopy I. Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lessor, D.L.; Hartman, J.S.; Gordon, R.L.

1979-02-01

The Nomarksi differential interference contrast microscope is examined as a tool for determination of metallic mirror surface topography. This discussion includes the development of an optical model for the Nomarski system, an examination of the key results of the model's application to sloped sample surfaces, and recommended procedures for implementation. The functional relationship is developed between image intensity and the component of surface slope along the Nomarski shear direction, the fixed parameters in the Nimarksi system, and the adjustable phase shifts related to Nomarski prism position. Equations are also developed to allow the determination of surface slope from relative imagemore » intensity when sample reflectively is uniform and slopes are small.« less

Influence of surface treatment on the in-vitro fracture resistance of zirconia-based all-ceramic anterior crowns.

PubMed

Schmitter, M; Lotze, G; Bömicke, W; Rues, S

2015-12-01

The purpose of this study was to assess the effect of surface treatment on the fracture resistance of zirconia-based all-ceramic anterior crowns. Sixty-four zirconia-based all-ceramic anterior crowns, veneered by use of a press-on technique, were produced. For 48 crowns intraoral adjustment was simulated (A-group), 16 crowns remained unadjusted (WA-group). The adjusted area was then treated in three ways: 1. no further surface treatment; 2. polishing, with irrigation, using polishers interspersed with diamond grit for ceramics; and 3. polishing and glaze firing. Half of the specimens were loaded until fracture in an universal testing device without artificial ageing; the other crowns underwent thermocycling and chewing simulation before ultimate-load testing. Explorative statistical analysis was performed by use of non-parametric and parametric tests. In addition, fracture-strength tests according to ISO 6872 were performed for veneer ceramic subjected to the different surface treatments. Finite element analysis was also conducted for the crowns, and surface roughness was measured. Crowns in the A-group were more sensitive to aging than crowns in the WA-group (p=0.038). Although both polishing and glaze firing slightly improved the fracture resistance of the specimens, the fracture resistance in the WA-group (initial fracture resistance (IFR): 652.0 ± 107.7N, remaining fracture resistance after aging (RFR): 560.6 ± 233.3N) was higher than the fracture resistance in the A-group (polished: IFR: 477.9 ± 108.8N, RFR: 386.0 ± 218.5N; glaze firing: IFR: 535.5 ± 128.0N, RFR: 388.6 ± 202.2N). Surface roughness without adjustment was Ra=0.1 μm; for adjustment but without further treatment it was Ra=1.4 μm; for adjustment and polishing it was Ra=0.3 μm; and for adjustment, polishing, and glazing it was Ra=0.6 μm. Stress distributions obtained by finite element analysis in combination with fracture strength tests showed that fractures most probably originated from the occlusal surface. To improve fracture resistance and reduce the incidence of failure, extensive occlusal adjustment of veneered anterior zirconia restorations should be avoided. Neither polishing nor glazing could restore the fracture resistance to the level maintained with unadjusted crowns. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

MOLA: Seasonal Snow Variations on Mars: Slow Flyover of the Martian North Pole

NASA Technical Reports Server (NTRS)

2001-01-01

MOLA: Seasonal Snow Variations on Mars: Slow Flyover of the Martian North Pole: False Color. This is a visualization of the topography near the Martian north pole as measured with the MOLA instrument. This particular animation shows a slow zoom to the surface of the pole, a flyover of the polar cap and a slow zoom out. The surface color is based on the elevation of the topography.

Mapping Ocean Surface Topography with a Synthetic-Aperture Interferometry Radar

NASA Technical Reports Server (NTRS)

Fu, Lee-Lueng; Rodriguez, Ernesto

2006-01-01

We propose to apply the technique of synthetic aperture radar interferometry to the measurement of ocean surface topography at spatial resolution approaching 1 km. The measurement will have wide ranging applications in oceanography, hydrology. and marine geophysics. The oceanographic and related societal applications are briefly discussed in the paper. To meet the requirements for oceanographic applications, the instrument must be flown in an orbit with proper sampling of ocean tides.

Towards Mapping the Ocean Surface Topography at 1 km Resolution

NASA Technical Reports Server (NTRS)

Fu, Lee-Lueng; Rodriquez, Ernesto

2006-01-01

We propose to apply the technique of synthetic aperture radar interferometry to the measurement of ocean surface topography at spatial resolution approaching 1 km. The measurement will have wide ranging applications in oceanography, hydrology, and marine geophysics. The oceanographic and related societal applications are briefly discussed in the paper. To meet the requirements for oceanographic applications, the instrument must be flown in an orbit with proper sampling of ocean tides.

High-resolution lidar topography of the Puget Lowland, Washington - A bonanza for earth science

USGS Publications Warehouse

Haugerud, R.A.; Harding, D.J.; Johnson, S.Y.; Harless, J.L.; Weaver, C.S.; Sherrod, B.L.

2003-01-01

More than 10,000 km2 of high-resolution, public-domain topography acquired by the Puget Sound Lidar Consortium is revolutionizing investigations of active faulting, continental glaciation, landslides, and surficial processes in the seismically active Puget Lowland. The Lowland-the population and economic center of the Pacific Northwest-presents special problems for hazards investigations, with its young glacial topography, dense forest cover, and urbanization. Lidar mapping during leaf-off conditions has led to a detailed digital model of the landscape beneath the forest canopy. The surface thus revealed contains a rich and diverse record of previously unknown surface-rupturing faults, deep-seated landslides, uplifted Holocene and Pleistocene beaches, and subglacial and periglacial features. More than half a dozen suspected postglacial fault scarps have been identified to date. Five scarps that have been trenched show evidence of large, Holocene, surface-rupturing earthquakes.

Influence of surface topography on depth profiles obtained with secondary-ion mass spectrometry

NASA Astrophysics Data System (ADS)

Walker, A. J.; Borchert, M. T.; Vriezema, C. J.; Zalm, P. C.

1990-11-01

Lithographically generated well-defined surface topography of submicron dimensions has been etched into silicon (100) previously implanted with 25 keV 11B to a fluence of 2×1014 atoms/cm2. The thus-obtained samples were depth profiled via secondary-ion mass spectrometry (SIMS). The boron concentration distributions measured were contrasted against those found on undisturbed flat parts of the target. From this intercomparison the otherwise trivial observation that surface topography causes profile distortion becomes suddenly alarming as an apparent improvement of depth resolution occurs. Scanning electron microscope images enable identification of the origin of this remarkable phenomenon. The present results imply that (i) the hitherto commonly accepted assumption in the interpretation of SIMS depth profiles that perceived gradients are never steeper than actual ones is subject to revision; (ii) it may prove very difficult, if not impossible, to construct SIMS equipment for reliable on-chip analysis of submicron details.

Impact of topography-radiation interaction on surface energy budget of the Tibetan Plateau in GCM simulations

NASA Astrophysics Data System (ADS)

Lee, W. L.; Liou, K. N.; Gu, Y.; Wang, C. C.; Wu, C. H.; Hsu, H. H.

2017-12-01

We have develop a parameterization to quantify the effect of 3-D topography on surface solar radiation, including multiple reflection and heating difference at sunward and shaded slopes of mountains. A series of sensitivity tests using NCAR CCSM4 with and without this parameterization have been carried out to investigate this effect in climate simulations. The result indicates that missing the 3-D radiation-topography interaction could be a key factor leading to cold biases over the Tibetan Plateau in winter in all of the CMIP5 models. Consequently, the snowmelt rate in the Tibetan Plateau could be underestimated in most future projections. In addition, the topographic effect can also increase the net surface solar radiation at the southern slope of the Himalayas in summer. The temporal and spatial distribution of monsoon precipitation and circulation could also be influenced.

Effect of fluoride prophylactic agents on the surface topography of NiTi and CuNiTi wires.

PubMed

Mane, Pratap P; Pawar, Renuka; Ganiger, Chanamallappa; Phaphe, Sandesh

2012-05-01

The aim of this study was to see the effect of topical fluoride on surface texture on nickel-titanium and copper-nickel-titanium orthodontic archwires. Preformed rectangular NiTi and CuNiTi wires were immersed in in fluoride solution and artificial saliva (control) for 90 minutes at 37°C. after immersion optical microscope was used to see the fluoride effect on the wire topography. The acidulated fluoride agents appeared to cause greater corrosive effects as compared to the neutral fluoride agents. The result suggest that using topical fluoride agents leads to corrosion of surface topography indirectly affecting the mechanical properties of the wire that will lead to prolonged orthodontic treatment. The use of topical fluoride agents has to be limited in patients with prolonged orthodontic treatment as it causes the corrosion of the NiTi and CuNiTi wires.

Identification of modes of fracture in a 2618-T6 aluminum alloy using stereophotogrammetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salas Zamarripa, A., E-mail: a.salaszamarripa@gmail.com; Pinna, C.; Brown, M.W.

2011-12-15

The identification and the development of a quantification technique of the modes of fracture in fatigue fracture surfaces of a 2618-T6 aluminum alloy were developed during this research. Fatigue tests at room and high temperature (230 Degree-Sign C) were carried out to be able to compare the microscopic fractographic features developed by this material under these testing conditions. The overall observations by scanning electron microscopy (SEM) of the fracture surfaces showed a mixture of transgranular and ductile intergranular fracture. The ductile intergranular fracture contribution appears to be more significant at room temperature than at 230 Degree-Sign C. A quantitative methodologymore » was developed to identify and to measure the contribution of these microscopic fractographic features. The technique consisted of a combination of stereophotogrammetry and image analysis. Stereo-pairs were randomly taken along the crack paths and were then analyzed using the profile module of MeX software. The analysis involved the 3-D surface reconstruction, the trace of primary profile lines in both vertical and horizontal directions within the stereo-pair area, the measurements of the contribution of the modes of fracture in each profile, and finally, the calculation of the average contribution in each stereo-pair. The technique results confirmed a higher contribution of ductile intergranular fracture at room temperature than at 230 Degree-Sign C. Moreover, there was no indication of a direct relationship between this contribution and the strain amplitudes range applied during the fatigue testing. - Highlights: Black-Right-Pointing-Pointer Stereophotogrammetry and image analysis as a measuring tool of modes of fracture in fatigue fracture surfaces. Black-Right-Pointing-Pointer A mixture of ductile intergranular and transgranular fracture was identified at room temperature and 230 Degree-Sign C testing. Black-Right-Pointing-Pointer Development of a quantitative methodology to obtain the percentage of modes of fracture within the fracture surface.« less

When the Desert Beetle Met the Carnivorous Plant: A Perfect Match for Droplet Growth and Shedding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aizenberg, Joanna; Park, Kyoo Chul; Kim, Philseok

2015-01-14

Phase change of vapor followed by coalescence and transport on ubiquitous bumped or curved surfaces is of fundamental importance for a wide range of phenomena and applications from water condensation on cold beverage bottles, to fogging on glasses and windshields, self-cleaning by jumping droplets, weathering, self-assembly, desalination, latent heat transfer, etc. Over the past decades, many attempts to understand and control the droplet growth dynamics and shedding of condensates on textured surfaces have focused on finding the role of micro/nanotexture combined with wettability. In particular, inspired by the Namib desert beetle bump structure, studies tested the effect of topography onmore » the preferential condensation. However, like the preferential condensation observed on flat surfaces, hybrid wettability rather than texture plays a major role; the role of bump topography on local preferential condensation has been unexplored and still not clearly understood. In addition, given that not only facilitating the droplet growth but also transporting the condensed droplets toward the desired reservoir is essential to make fresh sites for renucleation and regrowth of the droplets for enhancing condensation efficiency, the current hybrid-wettability- based design is not efficient to transport the condensates due to the high contact angle hysteresis created by highly wettable pinning points. Here we show that beetle-inspired bump topography leads faster localized condensation and transport of water. Employing simple analytic and more complicated numerical calculations, we reveal the detailed role of topography and predict the focused diffusion flux based on the distortion of concentration gradient around convex surface topography. We experimentally demonstrate the systematic understanding on the unseen effect of topographical parameters on faster droplet growth dynamics on various bump geometries. Further rational design of asymmetric topography and synergetic combination with slippery coating simultaneously enable both faster droplet growth and transport for applications including efficient water condensation.« less

An investigation of adhesive/adherend and fiber/matrix interactions. Part B: SEM/ESCA analysis of fracture surfaces

NASA Technical Reports Server (NTRS)

Beck, B.; Widyani, E.; Wightman, J. P.

1983-01-01

Adhesion was studied with emphasis on the characterization of surface oxide layers, the analysis of fracture surfaces, and the interaction of matrices and fibers. A number of surface features of the fractured lap shear samples were noted in the SEM photomicrographs including the beta phase alloy of the Ti 6-4 adherend, the imprint of the adherend on the adhesive failure surface, increased void density for high temperature samples, and the alumina filler particles. Interfacial failure of some of the fractured lap shear samples is invariably characterized by the appearance of an ESCA oxygen photopeak at 530.3 eV assigned to the surface oxide layer of Ti 6-4 adherend. The effect of grit blasting on carbon fiber composites is evident in the SEM analysis. A high surface fluorine concentration on the composite surface is reduced some ten fold by grit blasting.

Reversible switching of wetting properties and erasable patterning of polymer surfaces using plasma oxidation and thermal treatment

NASA Astrophysics Data System (ADS)

Rashid, Zeeshan; Atay, Ipek; Soydan, Seren; Yagci, M. Baris; Jonáš, Alexandr; Yilgor, Emel; Kiraz, Alper; Yilgor, Iskender

2018-05-01

Polymer surfaces reversibly switchable from superhydrophobic to superhydrophilic by exposure to oxygen plasma and subsequent thermal treatment are demonstrated. Two inherently different polymers, hydrophobic segmented polydimethylsiloxane-urea copolymer (TPSC) and hydrophilic poly(methyl methacrylate) (PMMA) are modified with fumed silica nanoparticles to prepare superhydrophobic surfaces with roughness on nanometer to micrometer scale. Smooth TPSC and PMMA surfaces are also used as control samples. Regardless of their chemical structure and surface topography, all surfaces display completely reversible wetting behavior changing from hydrophobic to hydrophilic and back for many cycles upon plasma oxidation followed by thermal annealing. Influence of plasma power, plasma exposure time, annealing temperature and annealing time on the wetting behavior of polymeric surfaces are investigated. Surface compositions, textures and topographies are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and white light interferometry (WLI), before and after oxidation and thermal annealing. Wetting properties of the surfaces are determined by measuring their static, advancing and receding water contact angle. We conclude that the chemical structure and surface topography of the polymers play a relatively minor role in reversible wetting behavior, where the essential factors are surface oxidation and migration of polymer molecules to the surface upon thermal annealing. Reconfigurable water channels on polymer surfaces are produced by plasma treatment using a mask and thermal annealing cycles. Such patterned reconfigurable hydrophilic regions can find use in surface microfluidics and optofluidics applications.

Theory of fracture mechanics based upon plasticity

NASA Technical Reports Server (NTRS)

Lee, J. D.

1976-01-01

A theory of fracture mechanics is formulated on the foundation of continuum mechanics. Fracture surface is introduced as an unknown quantity and is incorporated into boundary and initial conditions. Surface energy is included in the global form of energy conservation law and the dissipative mechanism is formulated into constitutive equations which indicate the thermodynamic irreversibility and the irreversibility of fracture process as well.

Preventing probe induced topography correlated artifacts in Kelvin Probe Force Microscopy.

PubMed

Polak, Leo; Wijngaarden, Rinke J

2016-12-01

Kelvin Probe Force Microscopy (KPFM) on samples with rough surface topography can be hindered by topography correlated artifacts. We show that, with the proper experimental configuration and using homogeneously metal coated probes, we are able to obtain amplitude modulation (AM) KPFM results on a gold coated sample with rough topography that are free from such artifacts. By inducing tip inhomogeneity through contact with the sample, clear potential variations appear in the KPFM image, which correlate with the surface topography and, thus, are probe induced artifacts. We find that switching to frequency modulation (FM) KPFM with such altered probes does not remove these artifacts. We also find that the induced tip inhomogeneity causes a lift height dependence of the KPFM measurement, which can therefore be used as a check for the presence of probe induced topography correlated artifacts. We attribute the observed effects to a work function difference between the tip and the rest of the probe and describe a model for such inhomogeneous probes that predicts lift height dependence and topography correlated artifacts for both AM and FM-KPFM methods. This work demonstrates that using a probe with a homogeneous work function and preventing tip changes is essential for KPFM on non-flat samples. From the three investigated probe coatings, PtIr, Au and TiN, the latter appears to be the most suitable, because of its better resistance against coating damage. Copyright © 2016 Elsevier B.V. All rights reserved.

Fractographic examination of racing greyhound central (navicular) tarsal bone failure surfaces using scanning electron microscopy.

PubMed

Tomlin, J L; Lawes, T J; Blunn, G W; Goodship, A E; Muir, P

2000-09-01

The greyhound is a fatigue fracture model of a short distance running athlete. Greyhounds have a high incidence of central (navicular) tarsal bone (CTB) fractures, which are not associated with overt trauma. We wished to determine whether these fractures occur because of accumulation of fatigue microdamage. We hypothesized that bone from racing dogs would show site-specific microdamage accumulation, causing predisposition to structural failure. We performed a fractographic examination of failure surfaces from fractured bones using scanning electron microscopy and assessed microcracking observed at the failure surface using a visual analog scale. Branching arrays of microcracks were seen in failure surfaces of CTB and adjacent tarsal bones, suggestive of compressive fatigue failure. Branching arrays of microcracks were particularly prevalent in remodeled trabecular bone that had become compact. CTB fractures showed increased microdamage when compared with other in vivo fractures (adjacent tarsal bone and long bone fractures), and ex vivo tarsal fractures induced by monotonic loading (P < 0.02). It was concluded that greyhound racing and training often results in CTB structural failure, because of accumulation and coalescence of branching arrays of fatigue microcracks, the formation of which appears to be predisposed to adapted bone.

The Effect of Surface Patterning on Corrosion Resistance of Biomedical Devices

NASA Astrophysics Data System (ADS)

Guo, Mengnan; Toloei, Alisina; Rotermund, Harm H.

2016-10-01

In this study, two styles of surface topographies have been created on stainless steel wires to test their corrosion resistance as simulated implanted biomedical devices. Grade 316 LVM stainless steel wire was initially polished to G1500 surface finish before treatment to produce the two different topographies: 1. Unidirectional roughness was created using SiC papers and 2. Various patterns were created with specific hole diameter and inter-hole spacing using focused ion beam (FIB). In order to simulate the environment of implanted biomedical devices, a three-electrode electrochemical cell with 0.9% (by mass) NaCl solution has been used to test the corrosion resistance of the samples by potentiodynamic polarization test method. SEM and EDS analyzed the appearance and chemical composition of different elements including oxygen on the surface. The potential of stable pitting, time related to the initiation of the stable pitting, and the highest corrosion current associated with stable pitting have been compared for samples with the two styles of topography. It was found that surfaces with patterns have a relatively higher pitting potential and it takes longer time to initiate stable pitting than the surface without any patterns.

In vitro rapid intraoral adjustment of porcelain prostheses using a high-speed dental handpiece.

PubMed

Song, Xiao-Fei; Yin, Ling; Han, Yi-Gang; Wang, Hui

2008-03-01

In vitro rapid intraoral adjustment of porcelain prostheses was conducted using a high-speed dental handpiece and diamond bur. The adjustment process was characterized by measurement of removal forces and energy, with scanning electron microscopic (SEM) observation of porcelain debris, surfaces and subsurface damage produced as a function of operational feed rate. Finite element analysis (FEA) was applied to evaluate subsurface stress distributions and degrees of subsurface damage. The results show that an increase in feed rate resulted in increases in both tangential and normal forces (analysis of variance (ANOVA), P<0.01). When the feed rate approached the highest rate of 60mm min(-1) at a fixed depth of cut of 100microm, the tangential force was nearly seven times that at the lowest feed rate of 15mm min(-1). Consequently, the specific removal energy increased significantly (ANOVA, P<0.01), and the maximum depth of subsurface damage obtained was approximately 110 and 120microm at the highest feed rate of 60mm min(-1) using SEM and FEA, respectively. The topographies of both the adjusted porcelain surfaces and the debris demonstrate microscopically that porcelain was removed via brittle fracture and plastic deformation. Clinicians must be cautious when pursuing rapid dental adjustments, because high operational energy, larger forces and severe surface and subsurface damage can be induced.

Calculation of Seismic Waves from Explosions with Tectonic Stresses and Topography

NASA Astrophysics Data System (ADS)

Stevens, J. L.; O'Brien, M.

2017-12-01

We investigate the effects of explosion depth, tectonic stresses and topography on seismic waves from underground nuclear explosions. We perform three-dimensional nonlinear calculations of an explosion at several depths in the topography of the North Korean test site. We also perform a large number of two-dimensional axisymmetric calculations of explosions at depths from 150 to 1000 meters in four earth structures, with compressive and tensile tectonic stresses and with no tectonic stresses. We use the representation theorem to propagate the results of these calculations and calculate seismic waves at regional and teleseismic distances. We find that P-waves are not strongly affected by any of these effects because the initial downgoing P-wave is unaffected by interaction with the free surface. Surface waves, however, are strongly affected by all of these effects. There is an optimal depth at which surface waves are maximized at the base of a mountain and at or slightly below normal containment depth. At deeper depths, increasing overburden pressure reduces the surface waves. At shallower depths, interaction with the free surface reduces the surface waves. For explosions inside a mountain, displacement of the sides of the mountain reduces surface waves. Compressive prestress reduces surface waves substantially, while tensile prestress increases surface waves. The North Korean explosions appear to be at an optimal depth, in a region of extension, and beneath a mountain, all of which increase surface wave amplitudes.

Effect of hydrogen on void initiation in tensile test of carbon steel JIS-S25C

NASA Astrophysics Data System (ADS)

Sugawa, S.; Tsutsumi, N.; Oda, K.

2018-06-01

In order to investigate the effect of hydrogen on tensile fracture mechanism of a carbon steel, tensile tests were conducted. Pre-strain specimens (0%, 5% and 10%) were used to study the effect of hydrogen content, since saturated hydrogen content in specimens increases in increasing dislocation density. The tensile strength and the yield stress of hydrogen specimens were almost the same as uncharged. In contrast, the reduction of area of hydrogen charged specimens was smaller than that of uncharged. To reveal the reasons of decrease of the reduction of area, the fracture surface and longitudinal cross section near the fracture surface were observed. On the fracture surface of uncharged specimens, only dimples were observed. On the other hand, dimples and flat fracture surface were observed on the fracture surface of hydrogen charged. On the longitudinal cross section of hydrogen charged specimens, many voids were observed compared to uncharged. From these observations, it is showed that hydrogen gives a rise to the increase of voids and the hydrogen charged specimens break without sufficient necking, thus hydrogen makes the reduction of area smaller.

Effects of topography on the interpretation of the deformation field of prominent volcanoes - Application to Etna

USGS Publications Warehouse

Cayol, V.; Cornet, F.H.

1998-01-01

We have investigated the effects of topography on the surface-deformation field of volcanoes. Our study provides limits to the use of classical half-space models. Considering axisymmetrical volcanoes, we show that interpreting ground-surface displacements with half-space models can lead to erroneous estimations of the shape of the deformation source. When the average slope of the flanks of a volcano exceeds 20??, tilting in the summit area is reversed to that expected for a flat surface. Thus, neglecting topography may lead to misinterpreting an inflation of the source as a deflation. Comparisons of Mogi's model with a three-dimensional model shows that ignoring topography may lead to an overestimate of the source-volume change by as much as 50% for a slope of 30??. This comparison also shows that the depths calculated by using Mogi's solution for prominent volcanoes should be considered as depths from the summit of the edifices. Finally, we illustrate these topographic effects by analyzing the deformation field measured by radar interferometry at Mount Etna during its 1991-1993 eruption. A three-dimensional modeling calculation shows that the flattening of the deflation field near the volcano's summit is probably a topographic effect.

Fracture-induced amorphization of polycrystalline SiO2 stishovite: a potential platform for toughening in ceramics

PubMed Central

Nishiyama, Norimasa; Wakai, Fumihiro; Ohfuji, Hiroaki; Tamenori, Yusuke; Murata, Hidenobu; Taniguchi, Takashi; Matsushita, Masafumi; Takahashi, Manabu; Kulik, Eleonora; Yoshida, Kimiko; Wada, Kouhei; Bednarcik, Jozef; Irifune, Tetsuo

2014-01-01

Silicon dioxide has eight stable crystalline phases at conditions of the Earth's rocky parts. Many metastable phases including amorphous phases have been known, which indicates the presence of large kinetic barriers. As a consequence, some crystalline silica phases transform to amorphous phases by bypassing the liquid via two different pathways. Here we show a new pathway, a fracture-induced amorphization of stishovite that is a high-pressure polymorph. The amorphization accompanies a huge volume expansion of ~100% and occurs in a thin layer whose thickness from the fracture surface is several tens of nanometers. Amorphous silica materials that look like strings or worms were observed on the fracture surfaces. The amount of amorphous silica near the fracture surfaces is positively correlated with indentation fracture toughness. This result indicates that the fracture-induced amorphization causes toughening of stishovite polycrystals. The fracture-induced solid-state amorphization may provide a potential platform for toughening in ceramics. PMID:25297473

Fracture-induced amorphization of polycrystalline SiO2 stishovite: a potential platform for toughening in ceramics.

PubMed

Nishiyama, Norimasa; Wakai, Fumihiro; Ohfuji, Hiroaki; Tamenori, Yusuke; Murata, Hidenobu; Taniguchi, Takashi; Matsushita, Masafumi; Takahashi, Manabu; Kulik, Eleonora; Yoshida, Kimiko; Wada, Kouhei; Bednarcik, Jozef; Irifune, Tetsuo

2014-10-09

Silicon dioxide has eight stable crystalline phases at conditions of the Earth's rocky parts. Many metastable phases including amorphous phases have been known, which indicates the presence of large kinetic barriers. As a consequence, some crystalline silica phases transform to amorphous phases by bypassing the liquid via two different pathways. Here we show a new pathway, a fracture-induced amorphization of stishovite that is a high-pressure polymorph. The amorphization accompanies a huge volume expansion of ~100% and occurs in a thin layer whose thickness from the fracture surface is several tens of nanometers. Amorphous silica materials that look like strings or worms were observed on the fracture surfaces. The amount of amorphous silica near the fracture surfaces is positively correlated with indentation fracture toughness. This result indicates that the fracture-induced amorphization causes toughening of stishovite polycrystals. The fracture-induced solid-state amorphization may provide a potential platform for toughening in ceramics.

Fracture Surface Analysis of Clinically Failed Fixed Partial Dentures

PubMed Central

Taskonak, B.; Mecholsky, J.J.; Anusavice, K.J.

2008-01-01

Ceramic systems have limited long-term fracture resistance, especially when they are used in posterior areas or for fixed partial dentures. The objective of this study was to determine the site of crack initiation and the causes of fracture of clinically failed ceramic fixed partial dentures. Six Empress 2® lithia-disilicate (Li2O·2SiO2)-based veneered bridges and 7 experimental lithia-disilicate-based non-veneered ceramic bridges were retrieved and analyzed. Fractography and fracture mechanics methods were used to estimate the stresses at failure in 6 bridges (50%) whose fracture initiated from the occlusal surface of the connectors. Fracture of 1 non-veneered bridge (8%) initiated within the gingival surface of the connector. Three veneered bridges fractured within the veneer layers. Failure stresses of the all-core fixed partial dentures ranged from 107 to 161 MPa. Failure stresses of the veneered fixed partial dentures ranged from 19 to 68 MPa. We conclude that fracture initiation sites are controlled primarily by contact damage. PMID:16498078

Fractography of induction-hardened steel fractured in fatigue and overload

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santos, C.G.; Laird, C.

1997-07-01

The fracture surfaces of induction-hardened steel specimens obtained from an auto axle were characterized, macroscopically and microscopically, after being fractured in fatigue and monotonic overload. Specimens were tested in cyclic three-point bending under load control, and the S-N curve was established for specimens that had been notched by spark machining to facilitate fractography. Scanning electron microscopy of the fractured surfaces obtained for lives spanning the range 17,000 to 418,000 cycles revealed diverse fracture morphologies, including intergranular fracture and transgranular fatigue fracture. The results are being offered to assist in the analysis of complex field failures in strongly hardened steel.

Terrain Classification on Venus from Maximum-Likelihood Inversion of Parameterized Models of Topography, Gravity, and their Relation

NASA Astrophysics Data System (ADS)

Eggers, G. L.; Lewis, K. W.; Simons, F. J.; Olhede, S.

2013-12-01

Venus does not possess a plate-tectonic system like that observed on Earth, and many surface features--such as tesserae and coronae--lack terrestrial equivalents. To understand Venus' tectonics is to understand its lithosphere, requiring a study of topography and gravity, and how they relate. Past studies of topography dealt with mapping and classification of visually observed features, and studies of gravity dealt with inverting the relation between topography and gravity anomalies to recover surface density and elastic thickness in either the space (correlation) or the spectral (admittance, coherence) domain. In the former case, geological features could be delineated but not classified quantitatively. In the latter case, rectangular or circular data windows were used, lacking geological definition. While the estimates of lithospheric strength on this basis were quantitative, they lacked robust error estimates. Here, we remapped the surface into 77 regions visually and qualitatively defined from a combination of Magellan topography, gravity, and radar images. We parameterize the spectral covariance of the observed topography, treating it as a Gaussian process assumed to be stationary over the mapped regions, using a three-parameter isotropic Matern model, and perform maximum-likelihood based inversions for the parameters. We discuss the parameter distribution across the Venusian surface and across terrain types such as coronoae, dorsae, tesserae, and their relation with mean elevation and latitudinal position. We find that the three-parameter model, while mathematically established and applicable to Venus topography, is overparameterized, and thus reduce the results to a two-parameter description of the peak spectral variance and the range-to-half-peak variance (in function of the wavenumber). With the reduction the clustering of geological region types in two-parameter space becomes promising. Finally, we perform inversions for the JOINT spectral variance of topography and gravity, in which the INITIAL loading by topography retains the Matern form but the FINAL topography and gravity are the result of flexural compensation. In our modeling, we pay explicit attention to finite-field spectral estimation effects (and their remedy via tapering), and to the implementation of statistical tests (for anisotropy, for initial-loading process correlation, to ascertain the proper density contrasts and interface depth in a two-layer model), robustness assessment and uncertainty quantification, as well as to algorithmic intricacies related to low-dimensional but poorly scaled maximum-likelihood inversions. We conclude that Venusian geomorphic terrains are well described by their 2-D topographic and gravity (cross-)power spectra, and the spectral properties of distinct geologic provinces on Venus are worth quantifying via maximum-likelihood-based methods under idealized three-parameter Matern distributions. Analysis of fitted parameters and the fitted-data residuals reveals natural variability in the (sub)surface properties on Venus, as well as some directional anisotropy. Geologic regions tend to cluster according to terrain type in our parameter space, which we analyze to confirm their shared geologic histories and utilize for guidance in ongoing mapping efforts of Venus and other terrestrial bodies.

Topographic characterisation of dental implants for commercial use

PubMed Central

Mendoza-Arnau, Amparo; Vallecillo-Capilla, Manuel-Francisco; Cabrerizo-Vílchez, Miguel-Ángel

2016-01-01

Background To characterize the surface topography of several dental implants for commercial use. Material and Methods Dental implants analyzed were Certain (Biomet 3i), Tissue Level (Straumann), Interna (BTI), MG-InHex (MozoGrau), SPI (Alphabio) and Hikelt (Bioner). Surface topography was ascertained using a confocal microscope with white light. Roughness parameters obtained were: Ra, Rq, Rv, Rp, Rt, Rsk and Rku. The results were analysed using single-factor ANOVA and Student-Neuman-Keuls(p<0.05) tests. Results Certain and Hikelt obtained the highest Ra and Rq scores, followed by Tissue Level. Interna and SPI obtained lower scores, and MG-InHex obtained the lowest score. Rv scores followed the same trend. Certain obtained the highest Rp score, followed by SPI and Hikelt, then Interna and Tissue Level. MG-InHex obtained the lowest scores. Certain obtained the highest Rt score, followed by Interna and Hikelt, then SPI and Tissue Level. The lowest scores were for MG-InHex. Rsk was negative (punctured surface) in the MG-InHex, SPI and Tissue Level systems, and positive (pointed surface) in the other systems. Rku was higher than 3 (Leptokurtic) in Tissue Level, Interna, MG-InHex and SPI, and lower than 3 (Platykurtic) in Certain and Hikelt. Conclusions The type of implant determines surface topography, and there are differences in the roughness parameters of the various makes of implants for clinical use. Key words:Implants for clinical use, topography, confocal microscopy. PMID:27475680

Charon's Surface in Detail

NASA Image and Video Library

2017-07-14

On July 14, 2015, NASA's New Horizons spacecraft made its historic flight through the Pluto system. This detailed, high-quality global mosaic of Pluto's largest moon, Charon, was assembled from nearly all of the highest-resolution images obtained by the Long-Range Reconnaissance Imager (LORRI) and the Multispectral Visible Imaging Camera (MVIC) on New Horizons. The mosaic is the most detailed and comprehensive global view yet of Charon's surface using New Horizons data. It includes topography data of the hemisphere visible to New Horizons during the spacecraft's closest approach. The topography is derived from digital stereo-image mapping tools that measure the parallax -- or the difference in the apparent relative positions -- of features on the surface obtained at different viewing angles during the encounter. Scientists use these parallax displacements of high and low terrain to estimate landform heights. The global mosaic has been overlain with transparent, colorized topography data wherever on the surface stereo data is available. Terrain south of about 30°S was in darkness leading up to and during the flyby, so is shown in black. All feature names on Pluto and Charon are informal. The global mosaic has been overlain with transparent, colorized topography data wherever on their surfaces stereo data is available. Standing out on Charon is the Caleuche Chasma ("C") in the far north, an enormous trough at least 350 kilometers (nearly 220 miles) long, and reaching 14 kilometers (8.5 miles) deep -- more than seven times as deep as the Grand Canyon. https://photojournal.jpl.nasa.gov/catalog/PIA21860

[The influence of autoclave sterilization on surface characteristics and cyclic fatigue resistance of 3 nickel-titanium rotary instruments].

PubMed

Li, Xiang-fen; Zheng, Ping; Xu, Li; Su, Qin

2015-12-01

To investigate the effects of autoclave sterilization on surface characteristics and cyclic fatigue resistance of 3 types of nickel-titanium rotary instruments (K3, Mtwo, ProTaper). Three brands of NiTi rotary endodontic instruments of the same size (tip diameter 0.25 mm and constant 0.06 taper) were selected: K3, Mtwo and Protaper (F2). 24 instruments for each brand were used to evaluate the effects of autoclave sterilization on inner character in the as-received condition and after subjection to 0, 1, 5, and 10 sterilization cycles (6 for each group). Time to fracture (TtF) from the start of the test to the moment of file breakage and the length of the fractured fragment were recorded. Means and standard deviations of TtF and fragment length were calculated. The data was analyzed with SPSS13.0 software package. Another 12 NiTi rotary instruments for each brand were used, 6 subjected to 10 autoclave sterilization cycles and the other as control. Scanning electron microscope was used to observe the changes in surface topography and inner character. For cyclic fatigue resistance, when sterilization was not performed, K3 showed the highest value of TtF means and ProTaper the lowest. The differences between each brand were statistically significant (P<0.05).When disinfection was performed, K3 brand showed greater fatigue resistance in comparison with the control when autoclave sterilization cycled 5 times and 10 times. The difference between 10 cycles of sterilization and the control was statistically significant (P<0.05); ProTaper brand showed significantly greater fatigue resistance in all the disinfected groups compared with the control (P<0.05) and 5 cycles of sterilization led to the greatest increment; The fatigue resistance of Mtwo brands increased with sterilization cycles and the difference between 5/10 cycles and the control were statistically significant (P<0.05). For surface characteristics, under scanning electron microscope, surface and inner imperfections in all instruments were intensified greatly after 10 cycles of sterilization. Cycle fatigue resistance is different among instruments of different brands. Autoclave sterilization may increase fatigue resistance of the 3 brands. Autoclave sterilization may increase the surface roughness and inner defects in cross section.

Role of Induced and Natural Imbibition in Frac Fluid Transport and Fate in Gas Shales, March 28-29, 2011

EPA Pesticide Factsheets

Hydraulic fracture modeling and fracture surface area calculations determined from pressure decay analysis and reservoir numerical flow simulation support estimates of created hydraulic fracture surface areas of 24-60 MM sq ft.

Simultaneous tuning of chemical composition and topography of copolymer surfaces: micelles as building blocks.

PubMed

Zhao, Ning; Zhang, Xiaoyan; Zhang, Xiaoli; Xu, Jian

2007-05-14

A simple method is described for controlling the surface chemical composition and topography of the diblock copolymer poly(styrene)-b-poly(dimethylsiloxane)(PS-b-PDMS) by casting the copolymer solutions from solvents with different selectivities. The surface morphology and chemical composition were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively, and the wetting behavior was studied by water contact angle (CA) and sliding angle (SA) and by CA hysteresis. Chemical composition and morphology of the surface depend on solvent properties, humidity of the air, solution concentration, and block lengths. If the copolymer is cast from a common solvent, the resultant surface is hydrophobic, with a flat morphology, and dominated by PDMS on the air side. From a PDMS-selective solvent, the surface topography depends on the morphology of the micelles. Starlike micelles give rise to a featureless surface nearly completely covered by PDMS, while crew-cut-like micelles lead to a rough surface with a hierarchical structure that consists partly of PDMS. From a PS-selective solvent, however, surface segregation of PDMS was restricted, and the surface morphology can be controlled by vapor-induced phase separation. On the basis of the tunable surface roughness and PDMS concentration on the air side, water repellency of the copolymer surface could be tailored from hydrophobic to superhydrophobic. In addition, reversible switching behavior between hydrophobic and superhydrophobic can be achieved by exposing the surface to solvents with different selectivities.

Measuring floodplain spatial patterns using continuous surface metrics at multiple scales

USGS Publications Warehouse

Scown, Murray W.; Thoms, Martin C.; DeJager, Nathan R.

2015-01-01

Interactions between fluvial processes and floodplain ecosystems occur upon a floodplain surface that is often physically complex. Spatial patterns in floodplain topography have only recently been quantified over multiple scales, and discrepancies exist in how floodplain surfaces are perceived to be spatially organised. We measured spatial patterns in floodplain topography for pool 9 of the Upper Mississippi River, USA, using moving window analyses of eight surface metrics applied to a 1 × 1 m2 DEM over multiple scales. The metrics used were Range, SD, Skewness, Kurtosis, CV, SDCURV,Rugosity, and Vol:Area, and window sizes ranged from 10 to 1000 m in radius. Surface metric values were highly variable across the floodplain and revealed a high degree of spatial organisation in floodplain topography. Moran's I correlograms fit to the landscape of each metric at each window size revealed that patchiness existed at nearly all window sizes, but the strength and scale of patchiness changed within window size, suggesting that multiple scales of patchiness and patch structure exist in the topography of this floodplain. Scale thresholds in the spatial patterns were observed, particularly between the 50 and 100 m window sizes for all surface metrics and between the 500 and 750 m window sizes for most metrics. These threshold scales are ~ 15–20% and 150% of the main channel width (1–2% and 10–15% of the floodplain width), respectively. These thresholds may be related to structuring processes operating across distinct scale ranges. By coupling surface metrics, multi-scale analyses, and correlograms, quantifying floodplain topographic complexity is possible in ways that should assist in clarifying how floodplain ecosystems are structured.

Process for structural geologic analysis of topography and point data

DOEpatents

Eliason, Jay R.; Eliason, Valerie L. C.

1987-01-01

A quantitative method of geologic structural analysis of digital terrain data is described for implementation on a computer. Assuming selected valley segments are controlled by the underlying geologic structure, topographic lows in the terrain data, defining valley bottoms, are detected, filtered and accumulated into a series line segments defining contiguous valleys. The line segments are then vectorized to produce vector segments, defining valley segments, which may be indicative of the underlying geologic structure. Coplanar analysis is performed on vector segment pairs to determine which vectors produce planes which represent underlying geologic structure. Point data such as fracture phenomena which can be related to fracture planes in 3-dimensional space can be analyzed to define common plane orientation and locations. The vectors, points, and planes are displayed in various formats for interpretation.

Anatomy of a Venusian hot spot - Geology, gravity, and mantle dynamics of Eistla Regio

NASA Technical Reports Server (NTRS)

Grimm, Robert E.; Phillips, Roger J.

1992-01-01

Results of a study of the western and central portions of the Venusian hot spot Eistla Regio are presented. Magellan radar images were mapped to elucidate the general geologic history of the region. Radial fracture systems both on the rises and volcanoes indicate that uplift and associated faulting accompanied volcanic construction. Prominent fracture zones strike WNW to NW, parallel to the long axis of the highlands. The largest of these, Guor Linea, exhibits a progressive deformation history that may include minor clockwise rotation in addition to bulk NNE-SSW extension. Pioneer Venus line-of-sight accelerations were inverted for vertical gravity which, when combined with topography, were used to solve for mass anomalies on the crust-mantle boundary and in the upper levels of the mantle convective system.

Morphological and structural changes at the Merapi lava dome monitored in 2012-15 using unmanned aerial vehicles (UAVs)

NASA Astrophysics Data System (ADS)

Darmawan, Herlan; Walter, Thomas R.; Brotopuspito, Kirbani Sri; Subandriyo; I Gusti Made Agung Nandaka

2018-01-01

Dome-building volcanoes undergo rapid and profound topographic changes that are important to quantify for the purposes of hazard assessment. However, as hazardous lava domes often develop on high-altitude volcanoes that exhibit steep-sided topography, it is challenging to obtain direct field access and thus to analyze these morphological and structural changes. Merapi Volcano in Indonesia is a type example of such a volcano, as soon after its 2010 eruption, a new lava dome developed. This dome was partially destroyed during six distinct steam-driven explosions that occurred between 2012 and 2014. Here, we investigate the topographic and structural changes associated with these six steam-driven explosions by comparing close-range photogrammetric data obtained before and after these explosions. To accomplish this, we performed two UAV campaigns in 2012 and 2015. By applying the Structure from Motion (SfM) technique, we are able to construct three-dimensional point clouds, assess their quality by comparing them to a terrestrial laser scanning (TLS) dataset, and generate high-resolution Digital Elevation Models (DEMs) and photomosaics. The comparison of these two DEMs and photomosaics reveals changes in topography and the appearance of fractures. In the 2012 dataset, we find a dense fracture network striking to the NNW-SSE. In the post-eruptive 2015 dataset, we see that this NNW-SSE fracture trend is much more strongly expressed; we also detect the formation of aligned and elongated explosion craters, which are associated with the removal of over 200,000 m3 of dome material, most of which ( 70%) was deposited outside the crater region. Therefore, this study suggests that the locations of the steam-driven explosions at Merapi Volcano were controlled by the reactivation of preexisting structures. Moreover, some of the newly developed and reactivated fractures delineate a block on the southern slope of the dome, which could become structurally unstable and potentially lead to rock avalanche hazards. This study therefore demonstrates the significance of characterizing structural fingerprints during the development of lava domes and exemplifies the value of topographic and fracture mapping, which is becoming increasingly feasible when using UAVs, even on high and steep stratovolcanoes. Fig. S2. The density of TLS point cloud dataset.

Glacial Inception in north-east Canada: The Role of Topography and Clouds

NASA Astrophysics Data System (ADS)

Birch, Leah; Tziperman, Eli; Cronin, Timothy

2016-04-01

Over the past 0.8 million years, ice ages have dominated Earth's climate on a 100 thousand year cycle. Interglacials were brief, sometimes lasting only a few thousand years, leading to the next inception. Currently, state-of-the-art global climate models (GCMs) are incapable of simulating the transition of Earth's climate from interglacial to glaciated. We hypothesize that this failure may be related to their coarse spatial resolution, which does not allow resolving the topography of inception areas, and their parameterized representation of clouds and atmospheric convection. To better understand the small scale topographic and cloud processes mis-represented by GCMs, we run the Weather Research and Forecasting model (WRF), which is a regional, cloud-resolving atmospheric model capable of a realistic simulation of the regional mountain climate and therefore of surface ice and snow mass balance. We focus our study on the mountain glaciers of Canada's Baffin Island, where geologic evidence indicates the last inception occurred at 115kya. We examine the sensitivity of mountain glaciers to Milankovitch Forcing, topography, and meteorology, while observing impacts of a cloud resolving model. We first verify WRF's ability to simulate present day climate in the region surrounding the Penny Ice Cap, and then investigate how a GCM-like biased representation of topography affects sensitivity of this mountain glacier to Milankovitch forcing. Our results show the possibility of ice cap growth on an initially snow-free landscape with realistic topography and insolation values from the last glacial inception. Whereas, smoothed topography as seen in GCMs has a negative surface mass balance, even with the relevant orbital parameter configuration. We also explore the surface mass balance feedbacks from an initially ice-covered Baffin Island and discuss the role of clouds and convection.

Magmatic intrusions in the lunar crust

NASA Astrophysics Data System (ADS)

Michaut, C.; Thorey, C.

2015-10-01

The lunar highlands are very old, with ages covering a timespan between 4.5 to 4.2 Gyr, and probably formed by flotation of light plagioclase minerals on top of the lunar magma ocean. The lunar crust provides thus an invaluable evidence of the geological and magmatic processes occurring in the first times of the terrestrial planets history. According to the last estimates from the GRAIL mission, the lunar primary crust is particularly light and relatively thick [1] This low-density crust acted as a barrier for the dense primary mantle melts. This is particularly evident in the fact that subsequent mare basalts erupted primarily within large impact basin: at least part of the crust must have been removed for the magma to reach the surface. However, the trajectory of the magma from the mantle to the surface is unknown. Using a model of magma emplacement below an elastic overlying layer with a flexural wavelength Λ, we characterize the surface deformations induced by the presence of shallow magmatic intrusions. We demonstrate that, depending on its size, the intrusion can show two different shapes: a bell shape when its radius is smaller than 4 times Λ or a flat top with small bended edges if its radius is larger than 4 times Λ[2]. These characteristic shapes for the intrusion result in characteristic deformations at the surface that also depend on the topography of the layer overlying the intrusion [3].Using this model we provide evidence of the presence of intrusions within the crust of the Moon as surface deformations in the form of low-slope lunar domes and floor-fractured craters. All these geological features have morphologies consistent with models of magma spreading at depth and deforming an overlying elastic layer. Further more,at floor-fractured craters, the deformation is contained within the crater interior, suggesting that the overpressure at the origin of magma ascent and intrusion was less than the pressure due to the weight of the crust removed by impact [3]. The pressure release due to material removal by impact is significant over a depth equivalent to the crater radius. Because many of these floor-fractured craters are relatively small, i.e. less than 20 to 30 km in radius, this observation suggests that the magma at the origin of the intrusion was already stored within or just below the crust, in deeper intrusions. Thus, a large fraction of the mantle melt might have been stored at depth below or within the light primary crust before reaching shallower layers. This, in turn, should have influenced the thermal and geological evolution of this crust.

Colorado Plateau rock strength, exhumation, and river knickzones - spatial datasets relating erodability to topographic metrics

NASA Astrophysics Data System (ADS)

Tressler, C.; Pederson, J. L.

2009-12-01

Bedrock resistance to erosion has a fundamental role in controlling topography and surface processes. This has been recognized since the birth of geomorphology, yet measurements and datasets quantifying rock strength are rare. This is despite it being an essential parameter in tectonic, fluvial, and hillslope process geomorphology, where erodability is commonly marginalized within the diffusivity constant, as well as the K coefficient in stream-power formulations and the channel-concavity and steepness indexes derived from it. The Colorado Plateau landscape, because of its semiarid climate and extensive exhumation, is strongly influenced by variations in bedrock. It is a prime setting to complete such a dataset of rock strength and analyze it in the context of erosion and topography because of both its historic scientific importance and the fact that all bedrock units are exposed for study. We are completing the measurement and mapping of the erodability of all major bedrock units at over 150 sites across the plateau through several approaches, including traditional Schmidt-hammer compressive strength, fracture spacing, and other characteristics associated with Selby rock-mass strength (RMS). These measures may specifically relate to erosion by mass-movement and fluvial plucking processes. Results highlight two problems with these basic data: they overestimate the strength of rock with massive bedding because of the heavy weighting of fracture spacing in Selby RMS, and they don’t include the extensive shale bedrock of the region. To address these issues, we are measuring sample tensile strength (Brazilian splitting test) to capture disintegration and fluvial abrasion erosion of massive units, and we are utilizing the stratigraphic proportion of shale within geologic units as a scaling factor in RMS. We are then exploring spatial relations of these strength measures to topography, exhumation, stream power, and steepness within the Colorado River drainage basin above Lake Mead. Using GIS, we map rock strength with respect to our existing estimate of mid-late Cenozoic exhumation, and calculate river-profile convexity and ks. Hydrogeomorphic models commonly assume that discharge along a system can be directly approximated through contributing area. However, the Colorado River system is an example where this assumption is invalid due to its downstream progression through increasingly arid terrain. This problem results in increasingly distorted values of long-profile metrics downstream. To address this, we develop an adjusted flow-accumulation grid that is calibrated using the pre-dam effective discharge of the Colorado River recorded at gauging stations. Initial results indicate rock strength and topographic metrics are strongly correlated in the middle-lower reaches of the plateau drainage. In this dry setting, we suggest topography and channel steepness are strongly linked to rock type. This linkage is less clear approaching lower order drainages and within the Rocky Mountain flank, where knickzones appear to insulate gentle headwaters. The pattern of exhumation across the region also suggests the primary signal of baselevel fall has passed through the heart of the Colorado Plateau, with possible transient knickzones along its mountainous rim.

INTERFRAGMENTARY SURFACE AREA AS AN INDEX OF COMMINUTION SEVERITY IN CORTICAL BONE IMPACT

PubMed Central

Beardsley, Christina L.; Anderson, Donald D.; Marsh, J. Lawrence; Brown, Thomas D.

2008-01-01

Summary A monotonic relationship is expected between energy absorption and fracture surface area generation for brittle solids, based on fracture mechanics principles. It was hypothesized that this relationship is demonstrable in bone, to the point that on a continuous scale, comminuted fractures created with specific levels of energy delivery could be discriminated from one another. Using bovine cortical bone segments in conjunction with digital image analysis of CT fracture data, the surface area freed by controlled impact fracture events was measured. The results demonstrated a statistically significant (p<0.0001) difference in measured de novo surface area between three specimen groups, over a range of input energies from 0.423 to 0.702 J/g. Local material properties were also incorporated into these measurements via CT Hounsfield intensities. This study confirms that comminution severity of bone fractures can indeed be measured on a continuous scale, based on energy absorption. This lays a foundation for similar assessments in human injuries. PMID:15885492

Adhesion and proliferation of OCT-1 osteoblast-like cells on micro- and nano-scale topography structured poly(L-lactide).

PubMed

Wan, Yuqing; Wang, Yong; Liu, Zhimin; Qu, Xue; Han, Buxing; Bei, Jianzhong; Wang, Shenguo

2005-07-01

The impact of the surface topography of polylactone-type polymer on cell adhesion was to be concerned because the micro-scale texture of a surface can provide a significant effect on the adhesion behavior of cells on the surface. Especially for the application of tissue engineering scaffold, the pore size could have an influence on cell in-growth and subsequent proliferation. Micro-fabrication technology was used to generate specific topography to investigate the relationship between the cells and surface. In this study the pits-patterned surfaces of polystyrene (PS) film with diameters 2.2 and 0.45 microm were prepared by phase-separation, and the corresponding scale islands-patterned PLLA surface was prepared by a molding technique using the pits-patterned PS as a template. The adhesion and proliferation behavior of OCT-1 osteoblast-like cells morphology on the pits- and islands-patterned surface were characterized by SEM observation, cell attachment efficiency measurement and MTT assay. The results showed that the cell adhesion could be enhanced on PLLA and PS surface with nano-scale and micro-scale roughness compared to the smooth surfaces of the PLLA and PS. The OCT-1 osteoblast-like cells could grow along the surface with two different size islands of PLLA and grow inside the micro-scale pits of the PS. However, the proliferation of cells on the micro- and nano-scale patterned surface has not been enhanced compared with the controlled smooth surface.

Gamma irradiation alters fatigue-crack behavior and fracture toughness in 1900H and GUR 1050 UHMWPE.

PubMed

Cole, Jantzen C; Lemons, Jack E; Eberhardt, Alan W

2002-01-01

Pitting and delamination remain causative factors of polyethylene failure in total knee replacement. Gamma irradiation induces cross linking in ultra-high-molecular-weight polyethylene, which has been shown to improve wear resistance. Irradiation may reduce fracture toughness and fatigue strength, however, and the effects of irradiation are dependent upon the resin, processing technique, and radiation dose. The effects of varying levels of gamma irradiation (0, 33, 66, and 100 kGy) on the fracture toughness and fatigue-crack resistance of UHMWPE, isostatically molded from 1900H and GUR 1050 resins, were examined. Paris law regressions were performed to quantify fatigue-crack propagation rates as functions of change in stress intensity, and J-integral methods were used to quantify the elastic-plastic fracture toughness. The results indicated that gamma irradiation reduced the resistance of both materials to fatigue-crack growth, and that the reductions were radiation dosage and resin dependent. Irradiation at any level was detrimental to the fracture toughness of the 1900H specimens. Irradiation at 33 kGy increased fracture toughness for the GUR 1050 specimens, and substantial reductions were observed only at the highest irradiation level. Scanning electron microscopy of the fracture surface revealed diamond-like fracture patterns of the nonirradiated specimens indicative of ductile, multilevel fracture. Pronounced striations were apparent on these fracture surfaces, oriented perpendicular to the direction of crack growth. The striations appeared as folds in surface layers of the GUR 1050 specimens. At the highest irradiation levels, the striations were nearly eliminated on the fracture surfaces of the 1900H specimens, and were markedly less severe for the GUR 1050. These results demonstrated that at higher irradiation levels the materials became more brittle in fatigue, with less ductile folding and tearing of the fracture surfaces. Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 559-566, 2002

Project GEOS-C. [designed to measure the topography of ocean surface and the sea state

NASA Technical Reports Server (NTRS)

1975-01-01

An oceanographic-geodetic satellite, designated Geodynamics Experimental Ocean Satellite-C (GEOS-C), an earth-orbiting spacecraft designed to measure precisely the topography of the ocean surface and the sea state (wave height, wave period, wave propagation direction) is described. Launch operations, spacecraft description, and mission objectives are included along with a brief flight history of the NASA satellite geodesy program. Principal investigations to be performed by the GEOS-C mission are discussed.

Complex Contact Angles Calculated from Capillary Rise Measurements on Rock Fracture Faces

NASA Astrophysics Data System (ADS)

Perfect, E.; Gates, C. H.; Brabazon, J. W.; Santodonato, L. J.; Dhiman, I.; Bilheux, H.; Bilheux, J. C.; Lokitz, B. S.

2017-12-01

Contact angles for fluids in unconventional reservoir rocks are needed for modeling hydraulic fracturing leakoff and subsequent oil and gas extraction. Contact angle measurements for wetting fluids on rocks are normally performed using polished flat surfaces. However, such prepared surfaces are not representative of natural rock fracture faces, which have been shown to be rough over multiple scales. We applied a variant of the Wilhelmy plate method for determining contact angle from the height of capillary rise on a vertical surface to the wetting of rock fracture faces by water in the presence of air. Cylindrical core samples (5.05 cm long x 2.54 cm diameter) of Mancos shale and 6 other rock types were investigated. Mode I fractures were created within the cores using the Brazilian method. Each fractured core was then separated into halves exposing the fracture faces. One fracture face from each rock type was oriented parallel to a collimated neutron beam in the CG-1D imaging instrument at ORNL's High Flux Isotope Reactor. Neutron radiography was performed using the multi-channel plate detector with a spatial resolution of 50 μm. Images were acquired every 60 s after a water reservoir contacted the base of the fracture face. The images were normalized to the initial dry condition so that the upward movement of water on the fracture face was clearly visible. The height of wetting at equilibrium was measured on the normalized images using ImageJ. Contact angles were also measured on polished flat surfaces using the conventional sessile drop method. Equilibrium capillary rise on the exposed fracture faces was up to 8.5 times greater than that predicted for polished flat surfaces from the sessile drop measurements. These results indicate that rock fracture faces are hyperhydrophilic (i.e., the height of capillary rise is greater than that predicted for a contact angle of zero degrees). The use of complex numbers permitted calculation of imaginary contact angles for such surfaces. This analysis yielded a continuum of contact angles (real above, and imaginary below, zero degrees) that can be used to investigate relationships with properties such surface roughness and porosity. It should be noted these are preliminary, unreplicated results and further research will be needed to verify them and refine the approach.

Impacts of land cover changes on climate trends in Jiangxi province China.

PubMed

Wang, Qi; Riemann, Dirk; Vogt, Steffen; Glaser, Rüdiger

2014-07-01

Land-use/land-cover (LULC) change is an important climatic force, and is also affected by climate change. In the present study, we aimed to assess the regional scale impact of LULC on climate change using Jiangxi Province, China, as a case study. To obtain reliable climate trends, we applied the standard normal homogeneity test (SNHT) to surface air temperature and precipitation data for the period 1951-1999. We also compared the temperature trends computed from Global Historical Climatology Network (GHCN) datasets and from our analysis. To examine the regional impacts of land surface types on surface air temperature and precipitation change integrating regional topography, we used the observation minus reanalysis (OMR) method. Precipitation series were found to be homogeneous. Comparison of GHCN and our analysis on adjusted temperatures indicated that the resulting climate trends varied slightly from dataset to dataset. OMR trends associated with surface vegetation types revealed a strong surface warming response to land barrenness and weak warming response to land greenness. A total of 81.1% of the surface warming over vegetation index areas (0-0.2) was attributed to surface vegetation type change and regional topography. The contribution of surface vegetation type change decreases as land cover greenness increases. The OMR precipitation trend has a weak dependence on surface vegetation type change. We suggest that LULC integrating regional topography should be considered as a force in regional climate modeling.

ATM Coastal Topography-Alabama 2001

USGS Publications Warehouse

Nayegandhi, Amar; Yates, Xan; Brock, John C.; Sallenger, A.H.; Bonisteel, Jamie M.; Klipp, Emily S.; Wright, C. Wayne

2009-01-01

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the Alabama coastline, acquired October 3-4, 2001. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative scanning Lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning Lidar system that measures high-resolution topography of the land surface, and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for pre-survey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography.

ATM Coastal Topography-Florida 2001: Eastern Panhandle

USGS Publications Warehouse

Yates, Xan; Nayegandhi, Amar; Brock, John C.; Sallenger, A.H.; Bonisteel, Jamie M.; Klipp, Emily S.; Wright, C. Wayne

2009-01-01

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the eastern Florida panhandle coastline, acquired October 2, 2001. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative scanning Lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning Lidar system that measures high-resolution topography of the land surface and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser-ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography.

A comparison of stereology, structural rigidity and a novel 3D failure surface analysis method in the assessment of torsional strength and stiffness in a mouse tibia fracture model.

PubMed

Wright, David A; Nam, Diane; Whyne, Cari M

2012-08-31

In attempting to develop non-invasive image based measures for the determination of the biomechanical integrity of healing fractures, traditional μCT based measurements have been limited. This study presents the development and evaluation of a tool for assessment of fracture callus mechanical properties through determination of the geometric characteristics of the fracture callus, specifically along the surface of failure identified during destructive mechanical testing. Fractures were created in tibias of ten male mice and subjected to μCT imaging and biomechanical torsion testing. Failure surface analysis, along with previously described image based measures was calculated using the μCT image data, and correlated with mechanical strength and stiffness. Three-dimensional measures along the surface of failure, specifically the surface area and torsional rigidity of bone, were shown to be significantly correlating with mechanical strength and stiffness. It was also shown that surface area of bone along the failure surface exhibits stronger correlations with both strength and stiffness than measures of average and minimum torsional rigidity of the entire callus. Failure surfaces observed in this study were generally oriented at 45° to the long axis of the bone, and were not contained exclusively within the callus. This work represents a proof of concept study, and shows the potential utility of failure surface analysis in the assessment of fracture callus stability. Copyright © 2012 Elsevier Ltd. All rights reserved.

EAARL coastal topography-Northern Outer Banks, North Carolina, post-Nor'Ida, 2009

USGS Publications Warehouse

Bonisteel-Cormier, J.M.; Nayegandhi, Amar; Wright, C.W.; Sallenger, A.H.; Brock, J.C.; Nagle, D.B.; Vivekanandan, Saisudha; Klipp, E.S.; Fredericks, Xan

2011-01-01

This DVD contains lidar-derived first-surface (FS) and bare-earth (BE) topography GIS datasets of a portion of the northern Outer Banks beachface in North Carolina. These datasets were acquired post-Nor'Ida on November 27 and 29, 2009.

Geologic structure of the eastern mare basins. [lunar basalts

NASA Technical Reports Server (NTRS)

Dehon, R. A.; Waskom, J. D.

1976-01-01

The thickness of mare basalts in the eastern maria are estimated and isopachs of the basalts are constructed. Sub-basalt basin floor topography is determined, and correlations of topographic variations of the surface with variations in basalt thickness or basin floor topography are investigated.

Atomic force microscopy study on topography of films produced by ion-based techniques

NASA Astrophysics Data System (ADS)

Wang, X.; Liu, X. H.; Zou, S. C.; Martin, P. J.; Bendavid, A.

1996-09-01

The evolution of surface morphologies of films prepared by ion-based deposition techniques has been investigated by atomic force microscopy. Two deposition processes, filtered arc deposition (FAD) and ion-beam-assisted deposition, where low-energy (<100 eV) ion irradiation and high-energy (several tens of keV) ion-beam bombardment concurrent with film growth were involved, respectively, have been employed to prepare TiN and Al films. Comparative studies on the effect of energetic ions on the development of topography have been performed between the low-ion-energy regime and high-ion-energy regime. In addition, the relationship between topography and mechanical properties of thin films has been revealed, by involving thin films prepared by thermal evaporation deposition (TED), where almost all depositing particles are neutral. In the images of the TED TiN and Al films, a large number of porous and deep boundaries between columnar grains was observed, suggesting a very rough and loose surface. In contrast, the FAD films exhibited much denser surface morphologies, although still columnar. The root-mean-square roughness of the FAD films was less than 1 Å. Hardness test and optical parameter measurement indicated that the FAD films were much harder and, in the case of optical films, much more transparent than the TED films, which was considered to arise from the denser surface morphologies rather than crystallization of the films. The high density and super smoothness of the FAD films, and the resultant mechanical and optical properties superior to those of the TED films, were attributed to the enhancement of surface migration of the deposited adatoms in the FAD process, which could provide intensive low-energy ion irradiation during film growth. As for topography modification by high-energy ion-beam bombardment concurrent with film growth, in addition to the increase of surface diffusion due to elastic collision and thermal spikes, physical sputtering must be considered while explaining the development of the film topography. Both surface migration enhancement and sputtering played important roles in the case of high-energy heavy-ion-beam bombardment, under which condition surface morphology characterized by dense columns with larger dimension and deep clean boundaries was formed. However, under high-energy light-ion-beam bombardment, the sputtering was dominant, and the variation of sputtering coefficient with position on the surface of growing film led to the formation of cones.

Spectral analysis of topography and gravity in the Basin and Range Province

USGS Publications Warehouse

Ricard, Y.; Froidevaux, C.; Simpson, R.

1987-01-01

A two-dimensional spectral analysis has been carried out for the topography and the Bouguer gravity anomaly of the Basin and Range Province in western North America. The aim was to investigate the possible presence of dominant wavelengths in the deformation pattern at the surface and at the depth of compensation. The results suggest that a 200-km wavelength in the deep compensating mass distribution has been inherited from an early tectonic phase of extension at an azimuth N65??E. The corresponding surface topography exhibits prominent overtones at wavelength of 100, 75, and possibly 45 km. It is argued that these characterize the non-linear rheology of the upper crust. The short wavelengths in the topography reflect the present phase of deformation, mixed with the results of the older deformations. These results point to a need to extend the physical models of lithospheric stretching beyond the presently available one-phase scenario. However, they show that the boudinage instability concept is consistent with the data. ?? 1987.

Synergetic topography and chemistry cues guiding osteogenic differentiation in bone marrow stromal cells through ERK1/2 and p38 MAPK signaling pathway.

PubMed

Zhang, Xinran; Li, Haotian; Lin, Chucheng; Ning, Congqin; Lin, Kaili

2018-01-30

Both the topographic surface and chemical composition modification can enhance rapid osteogenic differentiation and bone formation. Till now, the synergetic effects of topography and chemistry cues guiding biological responses have been rarely reported. Herein, the ordered micro-patterned topography and classically essential trace element of strontium (Sr) ion doping were selected to imitate topography and chemistry cues, respectively. The ordered micro-patterned topography on Sr ion-doped bioceramics was successfully duplicated using the nylon sieve as the template. Biological response results revealed that the micro-patterned topography design or Sr doping could promote cell attachment, ALP activity, and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). Most importantly, the samples both with micro-patterned topography and Sr doping showed the highest promotion effects, and could synergistically activate the ERK1/2 and p38 MAPK signaling pathways. The results suggested that the grafts with both specific topography and chemistry cues have synergetic effects on osteogenic activity of BMSCs and provide an effective approach to design functional bone grafts and cell culture substrates.

The Residual Polar Caps of Mars: Geological Differences and Possible Consequences

NASA Technical Reports Server (NTRS)

Thomas, P. C.; Sullivan, R.; Ingersoll, A. P.; Murray, B. C.; Danielson, G. E.; Herkenhoff, K. E.; Soderblom, L.; Malin, M. C.; Edgett, K. S.; James, P. B.

2000-01-01

The Martian polar regions have been known to have thick layered sequences (presumed to consist of silicates and ice), CO2 seasonal frost, and residual frosts that remain through the summer: H2O in the north, largely CO2 in the south. The relationship of the residual frosts to the underlying layered deposits could not be determined from Viking images. The Mars Orbiter Camera on Mars Global Surveyor has provided a 50-fold increase in resolution that shows more differences between the two poles. The north residual cap surface has rough topography of pits, cracks, and knobs, suggestive of ablational forms. This topography is less than a few meters in height, and grades in to surfaces exposing the layers underneath. In contrast, the south residual cap has distinctive collapse and possibly ablational topography emplaced in four or more layers, each approx. two meters thick. The top surface has polygonal depressions suggestive of thermal contraction cracks. The collapse and erosional forms include circular and cycloidal depressions, long sinuous troughs, and nearly parallel sets of troughs. The distinctive topography occurs throughout the residual cap area, but not outside it. Unconformities exposed in polar layers, or other layered materials, do not approximate the topography seen on the south residual cap. The coincidence of a distinct geologic feature, several layers modified by collapse, ablation, and mass movement with the residual cap indicates a distinct composition and/or climate compared to both the remainder of the south polar layered units and those in the north.

The in vivo blood compatibility of bio-inspired small diameter vascular graft: effect of submicron longitudinally aligned topography

PubMed Central

2013-01-01

Background Cardiovascular disease is the leading cause of deaths worldwide and the arterial reconstructive surgery remains the treatment of choice. Although large diameter vascular grafts have been widely used in clinical practices, there is an urgent need to develop a small diameter vascular graft with enhanced blood compatibility. Herein, we fabricated a small diameter vascular graft with submicron longitudinally aligned topography, which mimicked the tunica intima of the native arterial vessels and were tested in Sprague–Dawley (SD) rats. Methods Vascular grafts with aligned and smooth topography were prepared by electrospinning and were connected to the abdominal aorta of the SD rats to evaluate their blood compatibility. Graft patency and platelet adhesion were evaluated by color Doppler ultrasound and immunofluorescence respectively. Results We observed a significant higher patency rate (p = 0.021) and less thrombus formation in vascular graft with aligned topography than vascular graft with smooth topography. However, no significant difference between the adhesion rates on both vascular grafts (smooth/aligned: 0.35‰/0.12‰, p > 0.05) was observed. Moreover, both vascular grafts had few adherent activated platelets on the luminal surface. Conclusion Bionic vascular graft showed enhanced blood compatibility due to the effect of surface topography. Therefore, it has considerable potential for using in clinical application. PMID:24083888

Age-dependence of power spectral density and fractal dimension of bone mineralized matrix in atomic force microscope topography images: potential correlates of bone tissue age and bone fragility in female femoral neck trabeculae

PubMed Central

Milovanovic, Petar; Djuric, Marija; Rakocevic, Zlatko

2012-01-01

There is an increasing interest in bone nano-structure, the ultimate goal being to reveal the basis of age-related bone fragility. In this study, power spectral density (PSD) data and fractal dimensions of the mineralized bone matrix were extracted from atomic force microscope topography images of the femoral neck trabeculae. The aim was to evaluate age-dependent differences in the mineralized matrix of human bone and to consider whether these advanced nano-descriptors might be linked to decreased bone remodeling observed by some authors and age-related decline in bone mechanical competence. The investigated bone specimens belonged to a group of young adult women (n = 5, age: 20–40 years) and a group of elderly women (n = 5, age: 70–95 years) without bone diseases. PSD graphs showed the roughness density distribution in relation to spatial frequency. In all cases, there was a fairly linear decrease in magnitude of the power spectra with increasing spatial frequencies. The PSD slope was steeper in elderly individuals (−2.374 vs. −2.066), suggesting the dominance of larger surface morphological features. Fractal dimension of the mineralized bone matrix showed a significant negative trend with advanced age, declining from 2.467 in young individuals to 2.313 in the elderly (r = 0.65, P = 0.04). Higher fractal dimension in young women reflects domination of smaller mineral grains, which is compatible with the more freshly remodeled structure. In contrast, the surface patterns in elderly individuals were indicative of older tissue age. Lower roughness and reduced structural complexity (decreased fractal dimension) of the interfibrillar bone matrix in the elderly suggest a decline in bone toughness, which explains why aged bone is more brittle and prone to fractures. PMID:22946475

Age-dependence of power spectral density and fractal dimension of bone mineralized matrix in atomic force microscope topography images: potential correlates of bone tissue age and bone fragility in female femoral neck trabeculae.

PubMed

Milovanovic, Petar; Djuric, Marija; Rakocevic, Zlatko

2012-11-01

There is an increasing interest in bone nano-structure, the ultimate goal being to reveal the basis of age-related bone fragility. In this study, power spectral density (PSD) data and fractal dimensions of the mineralized bone matrix were extracted from atomic force microscope topography images of the femoral neck trabeculae. The aim was to evaluate age-dependent differences in the mineralized matrix of human bone and to consider whether these advanced nano-descriptors might be linked to decreased bone remodeling observed by some authors and age-related decline in bone mechanical competence. The investigated bone specimens belonged to a group of young adult women (n = 5, age: 20-40 years) and a group of elderly women (n = 5, age: 70-95 years) without bone diseases. PSD graphs showed the roughness density distribution in relation to spatial frequency. In all cases, there was a fairly linear decrease in magnitude of the power spectra with increasing spatial frequencies. The PSD slope was steeper in elderly individuals (-2.374 vs. -2.066), suggesting the dominance of larger surface morphological features. Fractal dimension of the mineralized bone matrix showed a significant negative trend with advanced age, declining from 2.467 in young individuals to 2.313 in the elderly (r = 0.65, P = 0.04). Higher fractal dimension in young women reflects domination of smaller mineral grains, which is compatible with the more freshly remodeled structure. In contrast, the surface patterns in elderly individuals were indicative of older tissue age. Lower roughness and reduced structural complexity (decreased fractal dimension) of the interfibrillar bone matrix in the elderly suggest a decline in bone toughness, which explains why aged bone is more brittle and prone to fractures. © 2012 The Authors Journal of Anatomy © 2012 Anatomical Society.

A sutureless aortic stent-graft based on a nitinol scaffold bonded to a compliant nanocomposite polymer is durable for 10 years in a simulated in vitro model.

PubMed

Desai, Mital; Bakhshi, Raheleh; Zhou, Xiang; Odlyha, Marianne; You, Zhong; Seifalian, Alexander M; Hamilton, George

2012-06-01

To physiologically test the durability of a sutureless aortic stent-graft based on nitinol bonded to polyhedral oligomeric silsesquioxane (POSS) and poly(carbonate-urea) urethane (PCU) for 10 years according to Food and Drug Administration guidelines. Aortic stent-grafts (n = 4) were tested in 37°C distilled water using simulated in vivo hydrodynamic pulse loading. After 400 million cycles, surface topography was assessed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Dynamic compliance was measured using a pulsatile flow phantom. Mechanical and elastic properties were determined by stress-strain studies and elastic deformation tests. Dynamic scanning calorimetry (DSC) and thermomechanical analysis (TMA) were used to assess thermal resistance. Comparison was made with a zero-cycled control. All stent-grafts successfully completed accelerated pulsatile fatigue at 94±14-mmHg pulse pressure. SEM images confirmed uniform surface topography without any fractures. FTIR showed increased intensity of -NHCO- bonds, but there was no significant sign of biodegradation. Tensile stress of fatigue-tested polymer compared favorably with the zero-cycled control at 50% to 500% strain (p = 0.69). At a mean pressure range of 60 to 120 mmHg, overall compliance of the fatigue-tested grafts was 3.48±1.27%mmHg(-1)×10(-2) with no significant difference compared to control (3.26±0.65%mmHg(-1)×10(-2); p = 0.47). DSC and TMA showed comparable thermotropic transition. Simulated physiological in vivo hydrodynamic loading has no significant degradative effect on an innovative sutureless stent-graft made from POSS-PCU nanocomposite polymer. Sutureless technology incorporating nitinol stents proved to be robust, with no separation over an accelerated 10-year cycle, which may allow development of durable stent-grafts with better compliance.

Comparative Tectonics of Europa and Ganymede

NASA Astrophysics Data System (ADS)

Pappalardo, R. T.; Collins, G. C.; Prockter, L. M.; Head, J. W.

2000-10-01

Europa and Ganymede are sibling satellites with tectonic similarities and differences. Ganymede's ancient dark terrain is crossed by furrows, probably related to ancient large impacts, and has been normal faulted to various degrees. Bright grooved is pervasively deformed at multiple scales and is locally highly strained, consistent with normal faulting of an ice-rich lithosphere above a ductile asthenosphere, along with minor horizontal shear. Little evidence has been identified for compressional structures. The relative roles of tectonism and icy cryovolcanism in creating bright grooved terrain is an outstanding issue. Some ridge and trough structures within Europa's bands show tectonic similarities to Ganymede's grooved terrain, specifically sawtooth structures resembling normal fault blocks. Small-scale troughs are consistent with widened tension fractures. Shearing has produced transtensional and transpressional structures in Europan bands. Large-scale folds are recognized on Europa, with synclinal small-scale ridges and scarps probably representing folds and/or thrust blocks. Europa's ubiquitous double ridges may have originated as warm ice upwelled along tidally heated fracture zones. The morphological variety of ridges and troughs on Europa imply that care must be taken in inferring their origin. The relative youth of Europa's surface means that the satellite has preserved near-pristine morphologies of many structures, though sputter erosion could have altered the morphology of older topography. Moderate-resolution imaging has revealed lesser apparent diversity in Ganymede's ridge and trough types. Galileo's 28th orbit has brought new 20 m/pixel imaging of Ganymede, allowing direct comparison to Europa's small-scale structures.

Surface self-potential patterns related to transmissive fracture trends during a water injection test

NASA Astrophysics Data System (ADS)

DesRoches, A. J.; Butler, K. E.; MacQuarrie, K. TB

2018-03-01

Variations in self-potential (SP) signals were recorded over an electrode array during a constant head injection test in a fractured bedrock aquifer. Water was injected into a 2.2 m interval isolated between two inflatable packers at 44 m depth in a vertical well. Negative SP responses were recorded on surface corresponding to the start of the injection period with strongest magnitudes recorded in electrodes nearest the well. SP response decreased in magnitude at electrodes further from the well. Deflation of the packer system resulted in a strong reversal in the SP signal. Anomalous SP patterns observed at surface at steady state were found to be aligned with dominant fracture strike orientations found within the test interval. Numerical modelling of fluid and current flow within a simplified fracture network showed that azimuthal patterns in SP are mainly controlled by transmissive fracture orientations. The strongest SP gradients occur parallel to hydraulic gradients associated with water flowing out of the transmissive fractures into the tighter matrix and other less permeable cross-cutting fractures. Sensitivity studies indicate that increasing fracture frequency near the well increases the SP magnitude and enhances the SP anomaly parallel to the transmissive set. Decreasing the length of the transmissive fractures leads to more fluid flow into the matrix and into cross-cutting fractures proximal to the well, resulting in a more circular and higher magnitude SP anomaly. Results from the field experiment and modelling provide evidence that surface-based SP monitoring during constant head injection tests has the ability to identify groundwater flow pathways within a fractured bedrock aquifer.

Failure Analysis on Tail Rotor Teeter Pivot Bolt on a Helicopter

NASA Astrophysics Data System (ADS)

Qiang, WANG; Zi-long, DONG

2018-03-01

Tail rotor teeter pivot bolt of a helicopter fractured when in one flight. Failure analysis on the bolt was finished in laboratory. Macroscopic observation of the tailor rotor teeter pivot bolt, macro and microscopic inspection on the fracture surface of the bolt was carried out. Chemical components and metallurgical structure was also carried out. Experiment results showed that fracture mode of the tail rotor teeter pivot bolt is fatigue fracture. Fatigue area is over 80% of the total fracture surface, obvious fatigue band characteristics can be found at the fracture face. According to the results were analyzed from the macroscopic and microcosmic aspects, fracture reasons of the tail rotor teeter pivot bolt were analyzed in detail

The impact of using area-averaged land surface properties —topography, vegetation condition, soil wetness—in calculations of intermediate scale (approximately 10 km 2) surface-atmosphere heat and moisture fluxes

NASA Astrophysics Data System (ADS)

Sellers, Piers J.; Heiser, Mark D.; Hall, Forrest G.; Verma, Shashi B.; Desjardins, Raymond L.; Schuepp, Peter M.; Ian MacPherson, J.

1997-03-01

It is commonly assumed that biophysically based soil-vegetation-atmosphere transfer (SVAT) models are scale-invariant with respect to the initial boundary conditions of topography, vegetation condition and soil moisture. In practice, SVAT models that have been developed and tested at the local scale (a few meters or a few tens of meters) are applied almost unmodified within general circulation models (GCMs) of the atmosphere, which have grid areas of 50-500 km 2. This study, which draws much of its substantive material from the papers of Sellers et al. (1992c, J. Geophys. Res., 97(D17): 19033-19060) and Sellers et al. (1995, J. Geophys. Res., 100(D12): 25607-25629), explores the validity of doing this. The work makes use of the FIFE-89 data set which was collected over a 2 km × 15 km grassland area in Kansas. The site was characterized by high variability in soil moisture and vegetation condition during the late growing season of 1989. The area also has moderate topography. The 2 km × 15 km 'testbed' area was divided into 68 × 501 pixels of 30 m × 30 m spatial resolution, each of which could be assigned topographic, vegetation condition and soil moisture parameters from satellite and in situ observations gathered in FIFE-89. One or more of these surface fields was area-averaged in a series of simulation runs to determine the impact of using large-area means of these initial or boundary conditions on the area-integrated (aggregated) surface fluxes. The results of the study can be summarized as follows: 1. analyses and some of the simulations indicated that the relationships describing the effects of moderate topography on the surface radiation budget are near-linear and thus largely scale-invariant. The relationships linking the simple ratio vegetation index ( SR), the canopy conductance parameter (▽ F) and the canopy transpiration flux are also near-linear and similarly scale-invariant to first order. Because of this, it appears that simple area-averaging operations can be applied to these fields with relatively little impact on the calculated surface heat flux. 2. The relationships linking surface and root-zone soil wetness to the soil surface and canopy transpiration rates are non-linear. However, simulation results and observations indicate that soil moisture variability decreases significantly as an area dries out, which partially cancels out the effects of these non-linear functions.In conclusion, it appears that simple averages of topographic slope and vegetation parameters can be used to calculate surface energy and heat fluxes over a wide range of spatial scales, from a few meters up to many kilometers at least for grassland sites and areas with moderate topography. Although the relationships between soil moisture and evapotranspiration are non-linear for intermediate soil wetnesses, the dynamics of soil drying act to progressively reduce soil moisture variability and thus the impacts of these non-linearities on the area-averaged surface fluxes. These findings indicate that we may be able to use mean values of topography, vegetation condition and soil moisture to calculate the surface-atmosphere fluxes of energy, heat and moisture at larger length scales, to within an acceptable accuracy for climate modeling work. However, further tests over areas with different vegetation types, soils and more extreme topography are required to improve our confidence in this approach.

Torsion fracture of carbon nanocoils

NASA Astrophysics Data System (ADS)

Yonemura, Taiichiro; Suda, Yoshiyuki; Tanoue, Hideto; Takikawa, Hirofumi; Ue, Hitoshi; Shimizu, Kazuki; Umeda, Yoshito

2012-10-01

We fix a carbon nanocoil (CNC) on a substrate in a focused ion beam instrument and then fracture the CNC with a tensile load. Using the CNC spring index, we estimate the maximum to average stress ratio on the fractured surface to range from 1.3 to 1.7, indicating stress concentration on the coil wire inner edge. Scanning electron microscopy confirms a hollow region on the inner edge of all fractured surfaces.

Effect of hot extrusion, other constituents, and temperature on the strength and fracture of polycrystalline MgO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rice, R.W.

Improved agreement was confirmed between the Petch intercept and single-crystal yield stresses at 22 C. Hot-extruded MgO crystal specimens stressed parallel with the resultant axial texture (1) gave the highest and least-scattered strength-grain size results at 22 C, (2) showed direct fractographic evidence of microplastic initiated fracture at 22 C and showed macroscopic yield at 1,315 and especially 1,540 C, and (3) fractured entirely via transgranular cleavage, except for intergranular failure initiation from one or a few grain boundary surfaces exposed on the subsequent fracture surface, mainly at 1,540 C. Hot-extruded, hot-pressed MgO billets gave comparable strength when fracture initiatedmore » transgranularly, but lower strength when fracture initiated from one or especially a few grain boundary surfaces exposed on the fracture. The extent and frequency of such boundary fracture increased with test temperature. While oxide additions of [<=] 5% or impurities in hot-pressed or hot-extruded MgO can make limited strength increases at larger grain sizes, those having limited solubility can limit strength at finer grain sizes, as can coarser surface finish. Overall, MgO strength is seen as a balance between flaw and microplastic controlled failure, with several parameters shifting the balance.« less

Surface properties of beached plastics.

PubMed

Fotopoulou, Kalliopi N; Karapanagioti, Hrissi K

2015-07-01

Studying plastic characteristics in the marine environment is important to better understand interaction between plastics and the environment. In the present study, high-density polyethylene (HDPE), polyethylene terephalate (PET), and polyvinyl chloride (PVC) samples were collected from the coastal environment in order to study their surface properties. Surface properties such as surface functional groups, surface topography, point of zero charge, and color change are important factors that change during degradation. Eroded HDPE demonstrated an altered surface topography and color and new functional groups. Eroded PET surface was uneven, yellow, and occasionally, colonized by microbes. A decrease in Fourier transform infrared (FTIR) peaks was observed for eroded PET suggesting that degradation had occurred. For eroded PVC, its surface became more lamellar and a new FTIR peak was observed. These surface properties were obtained due to degradation and could be used to explain the interaction between plastics, microbes, and pollutants.

Quaternary Landscape Evolution and the Surface Expression of Plume-Lithosphere Interactions in the Greater Yellowstone Area.

NASA Astrophysics Data System (ADS)

Guerrero, E.; Meigs, A.; Kirby, E.

2016-12-01

Numerous investigations demonstrate that mantle convective processes such as upwelling affect the surface topography of the overriding plate and propagates through the plate accompanying its lateral motion. This deformation signal is known as transient topography and is thought to occur in the North American plate as it passes over the Yellowstone hotspot. This work explores the sensitivity of the surface of Western North America by testing the hypothesis that advection of a transient topographic wave through the North American plate is driving post-Pliocene landscape evolution of the greater Yellowstone region as the plate passes over the mantle plume. Analysis of digital elevation data reveals an asymmetric topographic swell that has an amplitude of 400-1200 m and a wavelength of 600 km which was disentangled from overlapping signals preserved in the topography. A maximum uplift rate of 0.17 mm yr-1 leads the apex of the transient topography swell by nearly 100 km. This means that presently, the western edge of the Bighorn Basin is experiencing a surface uplift rate between 0.166 and 0.302 mm yr-1 which indicates 400-800m of surface uplift in the western edge of the basin since 3 Ma and a tilt of 0.3° and 0.5° away from Yellowstone. We reinterpret the drainage evolution and erosional story of the Bighorn Basin preserved by sequences of fluvial terraces in the Bighorn Basin based on this new deformation model. We integrate this new deformation model with mapping, dating, and paleoflow data into the post-Pliocene erosional story in the basin. The change from a northward drainage to an eastward drainage through stream capture, the lateral migration of the Bighorn river away from Yellowstone, and differential incision in the basin coincides with transient topography-forced deformation.

Effects of high-temperature gas dealkalization on surface mechanical properties of float glass

NASA Astrophysics Data System (ADS)

Senturk, Ufuk

The surface topography, and the near-surface structure and mechanical property changes on float glass, that was treated in atmospheres containing SOsb2, HCl, and 1,1 difluoroethane (DFE) gases, at temperatures in the glass transition region, were studied. Structure was investigated using surface sensitive infrared spectroscopy techniques (attenuated total reflectance (ATR) and diffuse reflectance (DRIFT)) and the topography was evaluated using atomic force microscopy (AFM). The results obtained from the two FTIR methods were in agreement with each other. Mechanical property characteristics of the surface were determined by measuring microhardness using a recording microindentation set-up. A simple analysis performed on the three hardness calculation methods-LVH, LVHsb2, and Lsb2VH-indicated that LVH and LVHsb2 are less effected by measurement errors and are better suited for the calculation of hardness. Contact damage characteristics of the treated glass was also studied by monitoring the crack initiation behavior during indentation, using acoustic emission. The results of the studies, aiming for the understanding of the structure, topography, and hardness property changes indicate that the treatment parameters-temperature, time, and treatment atmosphere conditions-are significant factors influencing these properties. The analysis of these results suggest a relation to exist between the three properties. This relation is used in understanding the surface mechanical properties of the treated float glasses. The difference in the thermal expansion coefficients between the dealkalized surface and bulk, the nature of surface structure changes, structural relaxation, surface water content, and glass transformation temperature are identified as the major factors having an influence on the properties. A model connecting these features is suggested. A difference in the structure, hardness, and topography on the air and tin sides of float glass is also shown to exist. The contact damage behavior of the treated surfaces is shown to differ from those of untreated surfaces, for SOsb2-treated float glass, where the crack initiation characteristics indicate crack formation from the surface and the indenter tip, different than the expected anomalous deformation. This behavior resembles that of a silica glass deformation on the surface, which is in agreement with the other foundations in this study.

Spectral Topography Generation for Arbitrary Grids

NASA Astrophysics Data System (ADS)

Oh, T. J.

2015-12-01

A new topography generation tool utilizing spectral transformation technique for both structured and unstructured grids is presented. For the source global digital elevation data, the NASA Shuttle Radar Topography Mission (SRTM) 15 arc-second dataset (gap-filling by Jonathan de Ferranti) is used and for land/water mask source, the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) 30 arc-second land water mask dataset v5 is used. The original source data is coarsened to a intermediate global 2 minute lat-lon mesh. Then, spectral transformation to the wave space and inverse transformation with wavenumber truncation is performed for isotropic topography smoothness control. Target grid topography mapping is done by bivariate cubic spline interpolation from the truncated 2 minute lat-lon topography. Gibbs phenomenon in the water region can be removed by overwriting ocean masked target coordinate grids with interpolated values from the intermediate 2 minute grid. Finally, a weak smoothing operator is applied on the target grid to minimize the land/water surface height discontinuity that might have been introduced by the Gibbs oscillation removal procedure. Overall, the new topography generation approach provides spectrally-derived, smooth topography with isotropic resolution and minimum damping, enabling realistic topography forcing in the numerical model. Topography is generated for the cubed-sphere grid and tested on the KIAPS Integrated Model (KIM).

Does Titan's Landscape Betray the Late Acquisitions of Its Current Atmosphere?

NASA Technical Reports Server (NTRS)

Moore, Jeffrey M.; Nimmo, F.

2012-01-01

Titan may have acquired its massive atmosphere relatively recently in solar system history. The sudden appearance of a thick atmosphere may have changed Titan's global topography. This change in global topography may be expressed in the latitudinal distribution of landform types across its surface.

Engineering design of sub-micron topographies for simultaneously adherent and reflective metal-polymer interfaces

NASA Technical Reports Server (NTRS)

Brown, Christopher A.

1993-01-01

The approach of the project is to base the design of multi-function, reflective topographies on the theory that topographically dependent phenomena react with surfaces and interfaces at certain scales. The first phase of the project emphasizes the development of methods for understanding the sizes of topographic features which influence reflectivity. Subsequent phases, if necessary, will address the scales of interaction for adhesion and manufacturing processes. A simulation of the interaction of electromagnetic radiation, or light, with a reflective surface is performed using specialized software. Reflectivity of the surface as a function of scale is evaluated and the results from the simulation are compared with reflectivity measurements made on multi-function, reflective surfaces.

Fractography of modern engineering materials: composites and metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masters, J.E.; Au, J.J.

1987-01-01

The fractographic analysis of fracture surfaces in composites and metals is discussed in reviews and reports of recent theoretical and experimental investigations. Topics addressed include fracture-surface micromorphology in engineering solids, SEM fractography of pure and mixed-mode interlaminar fractures in graphite/epoxy composites, determination of crack propagation directions in graphite/epoxy structures, and the fracture surfaces of irradiated composites. Consideration is given to fractographic feature identification and characterization by digital imaging analysis, fractography of pressure-vessel steel weldments, the micromechanisms of major/minor cycle fatigue crack growth in Inconel 718, and fractographic analysis of hydrogen-assisted cracking in alpha-beta Ti alloys.

Influence of dynamic topography on landscape evolution and passive continental margin stratigraphy

NASA Astrophysics Data System (ADS)

Ding, Xuesong; Salles, Tristan; Flament, Nicolas; Rey, Patrice

2017-04-01

Quantifying the interaction between surface processes and tectonics/deep Earth processes is one important aspect of landscape evolution modelling. Both observations and results from numerical modelling indicate that dynamic topography - a surface expression of time-varying mantle convection - plays a significant role in shaping landscape through geological time. Recent research suggests that dynamic topography also has non-negligible effects on stratigraphic architecture by modifying accommodation space available for sedimentation. In addition, dynamic topography influences the sediment supply to continental margins. We use Badlands to investigate the evolution of a continental-scale landscape in response to transient dynamic uplift or subsidence, and to model the stratigraphic development on passive continental margins in response to sea-level change, thermal subsidence and dynamic topography. We consider a circularly symmetric landscape consisting of a plateau surrounded by a gently sloping continental plain and a continental margin, and a linear wave of dynamic topography. We analyze the evolution of river catchments, of longitudinal river profiles and of the χ values to evaluate the dynamic response of drainage systems to dynamic topography. We calculate the amount of cumulative erosion and deposition, and sediment flux at shoreline position, as a function of precipitation rate and erodibility coefficient. We compute the stratal stacking pattern and Wheeler diagram on vertical cross-sections at the continental margin. Our results indicate that dynamic topography 1) has a considerable influence on drainage reorganization; 2) contributes to shoreline migration and the distribution of depositional packages by modifying the accommodation space; 3) affects sediment supply to the continental margin. Transient dynamic topography contributes to the migration of drainage divides and to the migration of the mainstream in a drainage basin. The dynamic uplift (respectively subsidence) of the source area results in an increase (respectively decrease) of sediment supply, while the dynamic uplift (respectively subsidence) of the continental margin leads to a decrease (respectively increase) in sedimentation.

The influence of chemical structure on thermal properties and surface morphology of polyurethane materials.

PubMed

Brzeska, Joanna; Morawska, Magda; Heimowska, Aleksandra; Sikorska, Wanda; Wałach, Wojciech; Hercog, Anna; Kowalczuk, Marek; Rutkowska, Maria

2018-01-01

The surface morphology and thermal properties of polyurethanes can be correlated to their chemical composition. The hydrophilicity, surface morphology, and thermal properties of polyurethanes (differed in soft segments and in linear/cross-linked structure) were investigated. The influence of poly([ R , S ]-3-hydroxybutyrate) presence in soft segments and blending of polyurethane with polylactide on surface topography were also estimated. The linear polyurethanes (partially crystalline) had the granular surface, whereas the surface of cross-linked polyurethanes (almost amorphous) was smooth. Round aggregates of polylactide un-uniformly distributed in matrix of polyurethane were clearly visible. It was concluded that some modification of soft segment (by mixing of poly([ R , S ]-3-hydroxybutyrate) with different polydiols and polytriol) and blending of polyurethanes with small amount of polylactide influence on crystallinity and surface topography of obtained polyurethanes.

Quantitative analysis of fracture surface by roughness and fractal method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, X.W.; Tian, J.F.; Kang, Y.

1995-09-01

In recent years there has been extensive research and great development in Quantitative Fractography, which acts as an integral part of fractographic analysis. A prominent technique for studying the fracture surface is based on fracture profile generation and the major means for characterizing the profile quantitatively are roughness and fractal methods. By this way, some quantitative indexes such as the roughness parameters R{sub L} for profile and R{sub S} for surface, fractal dimensions D{sub L} for profile and D{sub S} for surface can be measured. Given the relationships between the indexes and the mechanical properties of materials, it is possiblemore » to achieve the goal of protecting materials from fracture. But, as the case stands, the theory and experimental technology of quantitative fractography are still imperfect and remain to be studied further. Recently, Gokhale and Underwood et al have proposed an assumption-free method for estimating the surface roughness by vertically sectioning the fracture surface with sections at an angle of 120 deg with each other, which could be expressed as follows: R{sub S} = {ovr R{sub L}{center_dot}{Psi}} where {Psi} is the profile structure factor. This method is based on the classical sterological principles and verified with the aid of computer simulations for some ruled surfaces. The results are considered to be applicable to fracture surfaces with any arbitrary complexity and anisotropy. In order to extend the detail applications to this method in quantitative fractography, the authors made a study on roughness and fractal methods dependent on this method by performing quantitative measurements on some typical low-temperature impact fractures.« less

The support of long wavelength loads on Venus

NASA Astrophysics Data System (ADS)

Benerdt, W. B.; Saunders, R. S.

1985-04-01

One of the great surprises of the Pioneer Venus mission was the high degree of correlation between topography and gravity found at all wavelengths. This implies a close relationship between topography and lateral subsurface density anomalies, such as those due to passive or dynamic compensation. Sleep-Phillips type compensation model with a variable crustal thickness and a variable upper mantle density was developed. The thin shell theory was used to investigate three end member cases: (1) loading by topographic construction, resulting in a downward deflection of the surface (no mantle support); (2) completely compensated support of a constructional load (no surface deflection); and (3) topography due entirely to upward deflection of the surface supported by a low density upper mantle (no surface load). In general, the models imply relatively thick crust and dense upper mantle for Ishtar Terra and Ovda Regio (western Aphrodite), thinned crust and buoyant upper mantle for Tethus Regio and regions near Sappho and Alpha Regio, and a nearly uniform crust with a buoyant upper mantle for Beta Regio and Atla Regio (eastern Aphrodite).

Neurogenic differentiation of human umbilical cord mesenchymal stem cells on aligned electrospun polypyrrole/polylactide composite nanofibers with electrical stimulation

NASA Astrophysics Data System (ADS)

Zhou, Junfeng; Cheng, Liang; Sun, Xiaodan; Wang, Xiumei; Jin, Shouhong; Li, Junxiang; Wu, Qiong

2016-09-01

Adult central nervous system (CNS) tissue has a limited capacity to recover after trauma or disease. Recent medical cell therapy using polymeric biomaterialloaded stem cells with the capability of differentiation to specific neural population has directed focuses toward the recovery of CNS. Fibers that can provide topographical, biochemical and electrical cues would be attractive for directing the differentiation of stem cells into electro-responsive cells such as neuronal cells. Here we report on the fabrication of an electrospun polypyrrole/polylactide composite nanofiber film that direct or determine the fate of mesenchymal stem cells (MSCs), via combination of aligned surface topography, and electrical stimulation (ES). The surface morphology, mechanical properties and electric properties of the film were characterized. Comparing with that on random surface film, expression of neurofilament-lowest and nestin of human umbilical cord mesenchymal stemcells (huMSCs) cultured on film with aligned surface topography and ES were obviously enhanced. These results suggest that aligned topography combining with ES facilitates the neurogenic differentiation of huMSCs and the aligned conductive film can act as a potential nerve scaffold.

The Support of Long Wavelength Loads on Venus

NASA Technical Reports Server (NTRS)

Benerdt, W. B.; Saunders, R. S.

1985-01-01

One of the great surprises of the Pioneer Venus mission was the high degree of correlation between topography and gravity found at all wavelengths. This implies a close relationship between topography and lateral subsurface density anomalies, such as those due to passive or dynamic compensation. Sleep-Phillips type compensation model with a variable crustal thickness and a variable upper mantle density was developed. The thin shell theory was used to investigate three end member cases: (1) loading by topographic construction, resulting in a downward deflection of the surface (no mantle support); (2) completely compensated support of a constructional load (no surface deflection); and (3) topography due entirely to upward deflection of the surface supported by a low density upper mantle (no surface load). In general, the models imply relatively thick crust and dense upper mantle for Ishtar Terra and Ovda Regio (western Aphrodite), thinned crust and buoyant upper mantle for Tethus Regio and regions near Sappho and Alpha Regio, and a nearly uniform crust with a buoyant upper mantle for Beta Regio and Atla Regio (eastern Aphrodite).

Fracture toughness of ultrashort pulse-bonded fused silica

NASA Astrophysics Data System (ADS)

Richter, S.; Naumann, F.; Zimmermann, F.; Tünnermann, A.; Nolte, S.

2016-02-01

We determined the bond interface strength of ultrashort pulse laser-welded fused silica for different processing parameters. To this end, we used a high repetition rate ultrashort pulse laser system to inscribe parallel welding lines with a specific V-shaped design into optically contacted fused silica samples. Afterward, we applied a micro-chevron test to measure the fracture toughness and surface energy of the laser-inscribed welding seams. We analyzed the influence of different processing parameters such as laser repetition rate and line separation on the fracture toughness and fracture surface energy. Welding the entire surface a fracture toughness of 0.71 {MPa} {m}^{1/2}, about 90 % of the pristine bulk material ({≈ } 0.8 {MPa} {m}^{1/2}), is obtained.

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material

PubMed Central

Valíček, Jan; Harničárová, Marta; Öchsner, Andreas; Hutyrová, Zuzana; Kušnerová, Milena; Tozan, Hakan; Michenka, Vít; Šepelák, Vladimír; Mitaľ, Dušan; Zajac, Jozef

2015-01-01

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ. PMID:28793645

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material.

PubMed

Valíček, Jan; Harničárová, Marta; Öchsner, Andreas; Hutyrová, Zuzana; Kušnerová, Milena; Tozan, Hakan; Michenka, Vít; Šepelák, Vladimír; Mitaľ, Dušan; Zajac, Jozef

2015-11-03

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ.

Correlation between surface topography and lubricant migration in steel sheets for the autobody manufacturing process

NASA Astrophysics Data System (ADS)

Benati, F.; Sacerdotti, F.; Griffiths, B. J.; Butler, C.; Karila, J. M.; Vermeulen, M.; Holtkamp, H.; Gatti, S.

2002-05-01

Material for the production of autobody panels is usually dispatched in the form of coils. Because of their weight, they tend to `compress' the lubricant applied for rust protection and some of it leaks from the coil. Those areas affected by lubricant starvation are known as `dry-spots' and are a cause of a number of product rejections during the subsequent forming operation. A test was deployed with the combined work of Ocas, CORUS IJmuiden and Renault that proved that surface topography controls, amongst other factors, affects lubricant migration. The test consists of compressing a stack of lubricated steel sheets at known pressure for a known time using different lubricants in different amounts. It was observed that, because of the `compression', the lubricant tends to migrate to the side of the sheet, and its migration was quantified using a Fischer Betascope MMS module. Analysis consisted of analysis of variance on several designs of experiments and subsequent correlation with surface topography 3D parameters. These experiments showed the importance of standard amplitude surface parameters and new closed area surface parameters to characterize lubricant migration under pressure.

Surface fault slip associated with the 2004 Parkfield, California, earthquake

USGS Publications Warehouse

Rymer, M.J.; Tinsley, J. C.; Treiman, J.A.; Arrowsmith, J.R.; Ciahan, K.B.; Rosinski, A.M.; Bryant, W.A.; Snyder, H.A.; Fuis, G.S.; Toke, N.A.; Bawden, G.W.

2006-01-01

Surface fracturing occurred along the San Andreas fault, the subparallel Southwest Fracture Zone, and six secondary faults in association with the 28 September 2004 (M 6.0) Parkfield earthquake. Fractures formed discontinuous breaks along a 32-km-long stretch of the San Andreas fault. Sense of slip was right lateral; only locally was there a minor (1-11 mm) vertical component of slip. Right-lateral slip in the first few weeks after the event, early in its afterslip period, ranged from 1 to 44 mm. Our observations in the weeks following the earthquake indicated that the highest slip values are in the Middle Mountain area, northwest of the mainshock epicenter (creepmeter measurements indicate a similar distribution of slip). Surface slip along the San Andreas fault developed soon after the mainshock; field checks in the area near Parkfield and about 5 km to the southeast indicated that surface slip developed more than 1 hr but generally less than 1 day after the event. Slip along the Southwest Fracture Zone developed coseismically and extended about 8 km. Sense of slip was right lateral; locally there was a minor to moderate (1-29 mm) vertical component of slip. Right-lateral slip ranged from 1 to 41 mm. Surface slip along secondary faults was right lateral; the right-lateral component of slip ranged from 3 to 5 mm. Surface slip in the 1966 and 2004 events occurred along both the San Andreas fault and the Southwest Fracture Zone. In 1966 the length of ground breakage along the San Andreas fault extended 5 km longer than that mapped in 2004. In contrast, the length of ground breakage along the Southwest Fracture Zone was the same in both events, yet the surface fractures were more continuous in 2004. Surface slip on secondary faults in 2004 indicated previously unmapped structural connections between the San Andreas fault and the Southwest Fracture Zone, further revealing aspects of the structural setting and fault interactions in the Parkfield area.

Microscopic asperity contact and deformation of ultrahigh molecular weight polyethylene bearing surfaces.

PubMed

Wang, F C; Jin, Z M; McEwen, H M J; Fisher, J

2003-01-01

The effect of the roughness and topography of ultrahigh molecular weight polyethylene (UHMWPE) bearing surfaces on the microscopic contact mechanics with a metallic counterface was investigated in the present study. Both simple sinusoidal roughness forms, with a wide range of amplitudes and wavelengths, and real surface topographies, measured before and after wear testing in a simple pin-on-plate machine, were considered in the theoretical analysis. The finite difference method was used to solve the microscopic contact between the rough UHMWPE bearing surface and a smooth hard counterface. The fast Fourier transform (FFT) was used to cope with the large number of mesh points required to represent the surface topography of the UHMWPE bearing surface. It was found that only isolated asperity contacts occurred under physiological loading, and the real contact area was only a small fraction of the nominal contact area. Consequently, the average contact pressure experienced at the articulating surfaces was significantly higher than the nominal contact pressure. Furthermore, it was shown that the majority of asperities on the worn UHMWPE pin were deformed in the elastic region, and consideration of the plastic deformation only resulted in a negligible increase in the predicted asperity contact area. Microscopic asperity contact and deformation mechanisms may play an important role in the understanding of the wear mechanisms of UHMWPE bearing surfaces.

Finite difference elastic wave modeling with an irregular free surface using ADER scheme

NASA Astrophysics Data System (ADS)

Almuhaidib, Abdulaziz M.; Nafi Toksöz, M.

2015-06-01

In numerical modeling of seismic wave propagation in the earth, we encounter two important issues: the free surface and the topography of the surface (i.e. irregularities). In this study, we develop a 2D finite difference solver for the elastic wave equation that combines a 4th- order ADER scheme (Arbitrary high-order accuracy using DERivatives), which is widely used in aeroacoustics, with the characteristic variable method at the free surface boundary. The idea is to treat the free surface boundary explicitly by using ghost values of the solution for points beyond the free surface to impose the physical boundary condition. The method is based on the velocity-stress formulation. The ultimate goal is to develop a numerical solver for the elastic wave equation that is stable, accurate and computationally efficient. The solver treats smooth arbitrary-shaped boundaries as simple plane boundaries. The computational cost added by treating the topography is negligible compared to flat free surface because only a small number of grid points near the boundary need to be computed. In the presence of topography, using 10 grid points per shortest shear-wavelength, the solver yields accurate results. Benchmark numerical tests using several complex models that are solved by our method and other independent accurate methods show an excellent agreement, confirming the validity of the method for modeling elastic waves with an irregular free surface.

Epidemiology of racing injuries in Thoroughbred racehorses with special reference to bone fractures: Japanese experience from the 1980s to 2000s

PubMed Central

MAEDA, Yousuke; HANADA, Michiko; OIKAWA, Masa-aki

2016-01-01

ABSTRACT This report describes the descriptive epidemiology of racing fractures that occurred from the 1980s to 2000s on racetracks of the Japan Racing Association (JRA). The incidence of racehorse fractures during flat racing was approximately 1–2%. Fractures occurring during a race are more likely to occur in a forelimb. Fractures mostly occur at the third and fourth corners of oval tracks and on the home stretch. They also occur more frequently at the time of changing the leading limb. Comparison of the incidence of racing fracture between before and after reconstruction of the geometrical configuration of a racetrack revealed that there was an outstanding reduction in the number of serious fractures in the year before and after reconstruction. It was postulated that the improvement in racing time, possibly influenced by reconstructing the geometrical configuration of the racetrack, was connected to the reduction in the number of fractures. Of non-biological race- and course-related factors, type of course (dirt or turf), track surface condition, differences between racecourses, and racing distance significantly influence racing time. By using an instrumented shoe, vertical ground reaction forces (VGRFs) on the forelimb during galloping and the relationships between a rough dirt and woodchip track surface and a smooth dirt and woodchip surface were measured. Relating the incidence of racing fractures with track conditions in general showed that track surface has significant effects on the incidence of fracture, with the incidence of fractures increasing as track conditions on dirt worsen and a tendency for the incidence of fractures to decrease as track conditions on turf worsen. It seems probable that track condition in general may affect the incidence of fracture. The incidence of fracture in horses during both racing and training decreased as the years progressed. PMID:27703403

Fluid-driven fracture and melt transport through lithosphere on earth and terrestrial planets

NASA Astrophysics Data System (ADS)

Fialko, Yuri Alex

Fluid-driven fracture is a fundamental geophysical phenomenon operating in planetary interiors on many scales. A few examples of geological processes involving fluid transport via self-induced fractures include melt segregation in the mantle, magma ascent through the lithosphere, crustal accretion at mid-ocean ridges and volcanic "hot spots", migration of metamorphic and sedimentary fluids in the crust, etc. Overall, fluid-driven (in particular, magma-driven) fracture plays a major role in chemical differentiation of the upper mantle. Because our ability to make direct observations of the dynamics and styles of fluid-driven fracture is quite limited, our understanding of this phenomenon relies on theoretical models that use fundamental physical principles and available field data to constrain the behavior of fluid-driven cracks at depth. This thesis proposes new and more accurate ways of theoretical and experimental description of magma transport in self-induced fractures, or dikes. Dike propagation is a complex process that involves elastic and inelastic deformation of the host rocks, rock fracture, viscous flow of magma, heat transfer, and phase transitions (e.g., rock crystallization and fusion, volatile exolution etc.). We consider relationships between different physical processes associated with magma transport in dikes by solving appropriate boundary value problems of continuum mechanics and heat and mass transfer. The first chapter of this thesis revises existing interpretations of available experimental data bearing on the role of fracture resistance in the overall energy balance during dike propagation. It is shown for the first time that the experimental data indicate that the rock tensile fracture energy, which is not a material property at elevated confining pressures, may substantially increase under in-situ stress conditions. The second chapter concentrates on the interaction between magma flow, heat transfer and phase changes associated with dike emplacement, and discusses some important implications of our results for the generation of the Earth's crust at mid-ocean ridges. In particular, we find that the thermal arrest lengths of typical mid-ocean ridge dikes are of the order of the wavelength of crustal thickness variations and transform fault spacing along slow spreading ridges. This suggests that thermal controls on the crustal melt delivery system could be an important factor in modulating these variations. The third chapter deals with fluid-mechanical aspects of lateral dike propagation in volcanic rift zones. We demonstrate the existence of a feedback between viscous pressure losses during magma transport at depth and the along-strike surface topography of a rift zone. Our estimated values of the along-strike slopes resulting from such a feedback are in general agreement with observations in Hawaiian rift zones. The fourth chapter explores mechanisms of emplacement of giant dike swarms that might have played a role in splitting continents and producing mass extinctions. We reconcile field observations of chilled margins, low crustal contamination, and large dike thicknesses with the theoretically inferred turbulent mode of magma flow in such dikes.

All Along the Fractures

NASA Image and Video Library

2015-09-30

This image from NASA Mars Reconnaissance Orbiter spacecraft provides information about erosion and movement of surface material, about wind and weather patterns, even about the soil grains and grain sizes. However, looking past the dunes, these images also reveal the nature of the substrate beneath. Within the spaces between the dunes, a resistant and highly fractured surface is revealed. The fractured ground is resistant to erosion by the wind, and suggests the material is bedrock that is now shattered by a history of bending stresses or temperature changes, such as cooling, for example. Alternately, the surface may be a sedimentary layer that was once wet and shrunk and fractured as it dried, like gigantic mud cracks. In either case, the relative small and indistinct fractures have trapped the dark dune sand marching overhead. Now the fractures have become quite distinct, allowing us to examine the orientation and spacing of the fractures to learn more about the processes that formed them. http://photojournal.jpl.nasa.gov/catalog/PIA19958

Impact Processes in the Solar System

NASA Technical Reports Server (NTRS)

Ahrens, Thomas J.

2004-01-01

Our laboratory has previously conducted impact fracture and dynamic failure tests. Polanskey and Ahrens [1990] mapped the fractures from a series of laboratory craters (Fig. 1) and Ahrens and Rubin [ 1993] inferred that the usually further extending radial cracks resulted from tensional failure during the compression of the shock propagation. The radial spreading induced by the particle velocity field caused the stresses perpendicular to the shock front to become sufficiently large and tensile. This induces "radial fractures." The concentric fractures are attributed to the tensional failure occurring after the initial compressive phase. Upon radial propagation of the stress wave the negative tension behind the stress-wave front caused failure along the quasi-spherical concentric fractures. The near-surface and spall fractures are attributed to the fractures described by Melosh [1984]. These are activated by impact and can launch relatively unshocked samples of planetary surfaces to speeds exceeding escape velocity. In the case of Mars, some of these surface samples presumably become the SNC (Mars) meteorites.

Use of surface and borehole geophysical surveys to determine fracture orientation and other site characteristics in crystalline bedrock terrain, Millville and Uxbridge, Massachusetts

USGS Publications Warehouse

Hansen, Bruce P.; Lane, John W.

1995-01-01

Four geophysical techniques were used to determine bedrock-fracture orientation and other site characteristics that can be used to determine ground-water movement and contaminant transport at a fractured crystalline bedrock site in Millville and Uxbridge, Massachusetts. Azimuthal seismic- refraction and azimuthal square-array direct-current resistivity surveys were conducted at three sites. Borehole-radar surveys were conducted in a cluster of three wells. Ground-penetrating radar surveys were conducted along roads in the study area. Azimuthal seismic-refraction data indicated a primary fracture strike between 56 and 101 degrees at three sites. Graphical and analytical analysis of azimuthal square-array resistivity data indicated a primary fracture strike from 45 to 90 degrees at three sites. Directional borehole-radar data from three wells indicated 46 fractures or fracture zones located as far as 147 feet from the surveyed wells. Patterns of low radar-wave velocity and high radar- wave attenuation from cross-hole radar surveys of two well pairs were interpreted as a planar fracture zone that strikes 297 degrees and dips 55 degrees south. Ground-penetrating radar surveys with 100-MHz antennas penetrated as much as 150 feet of bedrock where the bedrock surface was at or near land surface. Horizontal and subhorizontal fractures were observed on the ground-penetrating radar records at numerous locations. Correlation of data sets indicates good agreement and indicates primary high- angle fracturing striking east-northeast. Secondary bedrock porosity and average fracture aperture determined from square-array resistivity data averaged 0.0044 and 0.0071 foot. Depths to bedrock observed on the ground-penetrating radar records were 0 to 20 feet below land surface along most of the area surveyed. A bedrock depth from 45 to 50 feet below land surface was observed along one section of Conestoga Drive.

Encapsulated proppants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.

2018-01-30

A capsule for carrying a proppant for emplaced in a formation containing formation fluid by a hydraulic fracture operation using a fracturing fluid. The capsule includes a capsule body. The capsule body includes a proppant. There is a surface layer on the capsule body that is permeable to the formation fluid or the fracturing fluid or is permeable to both the formation fluid and the fracturing fluid. The proppant material is dry cement that interacts with the formation fluid or the fracturing fluid or both the formation fluid and the fracturing fluid that migrate through the surface layer and ismore » taken up by the dry cement causing the dry cement to harden.« less

Encapsulated proppants

DOEpatents

Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Roberts, Jeffery James; Spadaccini, Christopher M.; Stolaroff, Joshuah K.

2018-01-09

A capsule for carrying a proppant for emplaced in a formation containing formation fluid by a hydraulic fracture operation using a fracturing fluid. The capsule includes a capsule body. The capsule body includes a proppant. There is a surface layer on the capsule body that is permeable to the formation fluid or the fracturing fluid or is permeable to both the formation fluid and the fracturing fluid. The proppant material is dry cement that interacts with the formation fluid or the fracturing fluid or both the formation fluid and the fracturing fluid that migrate through the surface layer and is taken up by the dry cement causing the dry cement to harden.